diff --git a/ext/spl/spl_iterators.stub.php b/ext/spl/spl_iterators.stub.php
index 859a454b59113..9d80717f85d8f 100644
--- a/ext/spl/spl_iterators.stub.php
+++ b/ext/spl/spl_iterators.stub.php
@@ -4,28 +4,28 @@
 
 class EmptyIterator implements Iterator
 {
-    /** @return mixed */
-    public function current() {}
+    /** @tentative-return-type */
+    public function current(): never {}
 
-    /** @return void */
-    public function next() {}
+    /** @tentative-return-type */
+    public function next(): void {}
 
-    /** @return mixed */
-    public function key() {}
+    /** @tentative-return-type */
+    public function key(): never {}
 
-    /** @return bool */
-    public function valid() {}
+    /** @tentative-return-type */
+    public function valid(): bool {}
 
-    /** @return void */
-    public function rewind() {}
+    /** @tentative-return-type */
+    public function rewind(): void {}
 }
 
 class CallbackFilterIterator extends FilterIterator
 {
     public function __construct(Iterator $iterator, callable $callback) {}
 
-    /** @return bool */
-    public function accept() {}
+    /** @tentative-return-type */
+    public function accept(): bool {}
 }
 
 class RecursiveCallbackFilterIterator extends CallbackFilterIterator implements RecursiveIterator
@@ -33,132 +33,132 @@ class RecursiveCallbackFilterIterator extends CallbackFilterIterator implements
     public function __construct(RecursiveIterator $iterator, callable $callback) {}
 
     /**
-     * @return bool
+     * @tentative-return-type
      * @implementation-alias RecursiveFilterIterator::hasChildren
      */
-    public function hasChildren() {}
+    public function hasChildren(): bool {}
 
-    /** @return RecursiveCallbackFilterIterator */
-    public function getChildren() {}
+    /** @tentative-return-type */
+    public function getChildren(): RecursiveCallbackFilterIterator {}
 }
 
 interface RecursiveIterator extends Iterator
 {
-    /** @return bool */
-    public function hasChildren();
+    /** @tentative-return-type */
+    public function hasChildren(): bool;
 
-    /** @return RecursiveIterator|null */
-    public function getChildren();
+    /** @tentative-return-type */
+    public function getChildren(): ?RecursiveIterator;
 }
 
 class RecursiveIteratorIterator implements OuterIterator
 {
     public function __construct(Traversable $iterator, int $mode = RecursiveIteratorIterator::LEAVES_ONLY, int $flags = 0) {}
 
-    /** @return void */
-    public function rewind() {}
+    /** @tentative-return-type */
+    public function rewind(): void {}
 
-    /** @return bool */
-    public function valid() {}
+    /** @tentative-return-type */
+    public function valid(): bool {}
 
-    /** @return mixed */
-    public function key() {}
+    /** @tentative-return-type */
+    public function key(): mixed {}
 
-    /** @return mixed */
-    public function current() {}
+    /** @tentative-return-type */
+    public function current(): mixed {}
 
-    /** @return void */
-    public function next() {}
+    /** @tentative-return-type */
+    public function next(): void {}
 
-    /** @return int */
-    public function getDepth() {}
+    /** @tentative-return-type */
+    public function getDepth(): int {}
 
-    /** @return RecursiveIterator|null */
-    public function getSubIterator(?int $level = null) {}
+    /** @tentative-return-type */
+    public function getSubIterator(?int $level = null): ?RecursiveIterator {}
 
-    /** @return RecursiveIterator */
-    public function getInnerIterator() {}
+    /** @tentative-return-type */
+    public function getInnerIterator(): RecursiveIterator {}
 
-    /** @return void */
-    public function beginIteration() {}
+    /** @tentative-return-type */
+    public function beginIteration(): void {}
 
-    /** @return void */
-    public function endIteration() {}
+    /** @tentative-return-type */
+    public function endIteration(): void {}
 
-    /** @return bool|null */
-    public function callHasChildren() {}
+    /** @tentative-return-type */
+    public function callHasChildren(): bool {}
 
-    /** @return RecursiveIterator|null */
-    public function callGetChildren() {}
+    /** @tentative-return-type */
+    public function callGetChildren(): ?RecursiveIterator {}
 
-    /** @return void */
-    public function beginChildren() {}
+    /** @tentative-return-type */
+    public function beginChildren(): void {}
 
-    /** @return void */
-    public function endChildren() {}
+    /** @tentative-return-type */
+    public function endChildren(): void {}
 
-    /** @return void */
-    public function nextElement() {}
+    /** @tentative-return-type */
+    public function nextElement(): void {}
 
-    /** @return void */
-    public function setMaxDepth(int $maxDepth = -1) {}
+    /** @tentative-return-type */
+    public function setMaxDepth(int $maxDepth = -1): void {}
 
-    /** @return int|false */
-    public function getMaxDepth() {}
+    /** @tentative-return-type */
+    public function getMaxDepth(): int|false {}
 }
 
 interface OuterIterator extends Iterator
 {
-    /** @return Iterator|null */
-    public function getInnerIterator();
+    /** @tentative-return-type */
+    public function getInnerIterator(): ?Iterator;
 }
 
 class IteratorIterator implements OuterIterator
 {
     public function __construct(Traversable $iterator, ?string $class = null) {}
 
-    /** @return Iterator|null */
-    public function getInnerIterator() {}
+    /** @tentative-return-type */
+    public function getInnerIterator(): ?Iterator {}
 
-    /** @return void */
-    public function rewind() {}
+    /** @tentative-return-type */
+    public function rewind(): void {}
 
-    /** @return bool */
-    public function valid() {}
+    /** @tentative-return-type */
+    public function valid(): bool {}
 
-    /** @return mixed */
-    public function key() {}
+    /** @tentative-return-type */
+    public function key(): mixed {}
 
-    /** @return mixed */
-    public function current() {}
+    /** @tentative-return-type */
+    public function current(): mixed {}
 
-    /** @return void */
-    public function next() {}
+    /** @tentative-return-type */
+    public function next(): void {}
 }
 
 abstract class FilterIterator extends IteratorIterator
 {
-    /** @return bool */
-    abstract public function accept();
+    /** @tentative-return-type */
+    abstract public function accept(): bool;
 
     public function __construct(Iterator $iterator) {}
 
-    /** @return void */
-    public function rewind() {}
+    /** @tentative-return-type */
+    public function rewind(): void {}
 
-    /** @return void */
-    public function next() {}
+    /** @tentative-return-type */
+    public function next(): void {}
 }
 
 abstract class RecursiveFilterIterator extends FilterIterator implements RecursiveIterator
 {
     public function __construct(RecursiveIterator $iterator) {}
 
-    /** @return bool */
-    public function hasChildren() {}
+    /** @tentative-return-type */
+    public function hasChildren(): bool {}
 
-    /** @return RecursiveFilterIterator|null */
-    public function getChildren() {}
+    /** @tentative-return-type */
+    public function getChildren(): ?RecursiveFilterIterator {}
 }
 
 class ParentIterator extends RecursiveFilterIterator
@@ -166,156 +166,156 @@ class ParentIterator extends RecursiveFilterIterator
     public function __construct(RecursiveIterator $iterator) {}
 
     /**
-     * @return bool
+     * @tentative-return-type
      * @implementation-alias RecursiveFilterIterator::hasChildren
      */
-    public function accept() {}
+    public function accept(): bool {}
 }
 
 interface SeekableIterator extends Iterator
 {
-    /** @return void */
-    public function seek(int $offset);
+    /** @tentative-return-type */
+    public function seek(int $offset): void;
 }
 
 class LimitIterator extends IteratorIterator
 {
     public function __construct(Iterator $iterator, int $offset = 0, int $limit = -1) {}
 
-    /** @return void */
-    public function rewind() {}
+    /** @tentative-return-type */
+    public function rewind(): void {}
 
-    /** @return bool */
-    public function valid() {}
+    /** @tentative-return-type */
+    public function valid(): bool {}
 
-    /** @return void */
-    public function next() {}
+    /** @tentative-return-type */
+    public function next(): void {}
 
-    /** @return int */
-    public function seek(int $offset) {}
+    /** @tentative-return-type */
+    public function seek(int $offset): int {}
 
-    /** @return int */
-    public function getPosition() {}
+    /** @tentative-return-type */
+    public function getPosition(): int {}
 }
 
 class CachingIterator extends IteratorIterator implements ArrayAccess, Countable, Stringable
 {
     public function __construct(Iterator $iterator, int $flags = CachingIterator::CALL_TOSTRING) {}
 
-    /** @return void */
-    public function rewind() {}
+    /** @tentative-return-type */
+    public function rewind(): void {}
 
-    /** @return bool */
-    public function valid() {}
+    /** @tentative-return-type */
+    public function valid(): bool {}
 
-    /** @return void */
-    public function next() {}
+    /** @tentative-return-type */
+    public function next(): void {}
 
-    /** @return bool */
-    public function hasNext() {}
+    /** @tentative-return-type */
+    public function hasNext(): bool {}
 
     public function __toString(): string {}
 
-    /** @return int */
-    public function getFlags() {}
+    /** @tentative-return-type */
+    public function getFlags(): int {}
 
-    /** @return void */
-    public function setFlags(int $flags) {}
+    /** @tentative-return-type */
+    public function setFlags(int $flags): void {}
 
     /**
      * @param string $key
-     * @return mixed
+     * @tentative-return-type
      */
-    public function offsetGet($key) {}
+    public function offsetGet($key): mixed {}
 
     /**
      * @param string $key
-     * @return void
+     * @tentative-return-type
      */
-    public function offsetSet($key, mixed $value) {}
+    public function offsetSet($key, mixed $value): void {}
 
     /**
      * @param string $key
-     * @return void
+     * @tentative-return-type
      */
-    public function offsetUnset($key) {}
+    public function offsetUnset($key): void {}
 
     /**
      * @param string $key
-     * @return bool
+     * @tentative-return-type
      */
-    public function offsetExists($key) {}
+    public function offsetExists($key): bool {}
 
-    /** @return array */
-    public function getCache() {}
+    /** @tentative-return-type */
+    public function getCache(): array {}
 
-    /** @return int */
-    public function count() {}
+    /** @tentative-return-type */
+    public function count(): int {}
 }
 
 class RecursiveCachingIterator extends CachingIterator implements RecursiveIterator
 {
     public function __construct(Iterator $iterator, int $flags = RecursiveCachingIterator::CALL_TOSTRING) {}
 
-    /** @return bool */
-    public function hasChildren() {}
+    /** @tentative-return-type */
+    public function hasChildren(): bool {}
 
-    /** @return RecursiveCachingIterator|null */
-    public function getChildren() {}
+    /** @tentative-return-type */
+    public function getChildren(): ?RecursiveCachingIterator {}
 }
 
 class NoRewindIterator extends IteratorIterator
 {
     public function __construct(Iterator $iterator) {}
 
-    /** @return void */
-    public function rewind() {}
+    /** @tentative-return-type */
+    public function rewind(): void {}
 
-    /** @return bool */
-    public function valid() {}
+    /** @tentative-return-type */
+    public function valid(): bool {}
 
-    /** @return mixed */
-    public function key() {}
+    /** @tentative-return-type */
+    public function key(): mixed {}
 
-    /** @return mixed */
-    public function current() {}
+    /** @tentative-return-type */
+    public function current(): mixed {}
 
-    /** @return void */
-    public function next() {}
+    /** @tentative-return-type */
+    public function next(): void {}
 }
 
 class AppendIterator extends IteratorIterator
 {
     public function __construct() {}
 
-    /** @return void */
-    public function append(Iterator $iterator) {}
+    /** @tentative-return-type */
+    public function append(Iterator $iterator): void {}
 
-    /** @return void */
-    public function rewind() {}
+    /** @tentative-return-type */
+    public function rewind(): void {}
 
-    /** @return bool */
-    public function valid() {}
+    /** @tentative-return-type */
+    public function valid(): bool {}
 
-    /** @return mixed */
-    public function current() {}
+    /** @tentative-return-type */
+    public function current(): mixed {}
 
-    /** @return void */
-    public function next() {}
+    /** @tentative-return-type */
+    public function next(): void {}
 
-    /** @return int|null */
-    public function getIteratorIndex() {}
+    /** @tentative-return-type */
+    public function getIteratorIndex(): ?int {}
 
-    /** @return ArrayIterator */
-    public function getArrayIterator() {}
+    /** @tentative-return-type */
+    public function getArrayIterator(): ArrayIterator {}
 }
 
 class InfiniteIterator extends IteratorIterator
 {
     public function __construct(Iterator $iterator) {}
 
-    /** @return void */
-    public function next() {}
+    /** @tentative-return-type */
+    public function next(): void {}
 }
 
 class RegexIterator extends FilterIterator
@@ -324,46 +324,46 @@ class RegexIterator extends FilterIterator
 
     public function __construct(Iterator $iterator, string $pattern, int $mode = RegexIterator::MATCH, int $flags = 0, int $pregFlags = 0) {}
 
-    /** @return bool */
-    public function accept() {}
+    /** @tentative-return-type */
+    public function accept(): bool {}
 
-    /** @return int */
-    public function getMode() {}
+    /** @tentative-return-type */
+    public function getMode(): int {}
 
-    /** @return void */
-    public function setMode(int $mode) {}
+    /** @tentative-return-type */
+    public function setMode(int $mode): void {}
 
-    /** @return int */
-    public function getFlags() {}
+    /** @tentative-return-type */
+    public function getFlags(): int {}
 
-    /** @return void */
-    public function setFlags(int $flags) {}
+    /** @tentative-return-type */
+    public function setFlags(int $flags): void {}
 
-    /** @return string */
-    public function getRegex() {}
+    /** @tentative-return-type */
+    public function getRegex(): string {}
 
-    /** @return int */
-    public function getPregFlags() {}
+    /** @tentative-return-type */
+    public function getPregFlags(): int {}
 
-    /** @return void */
-    public function setPregFlags(int $pregFlags) {}
+    /** @tentative-return-type */
+    public function setPregFlags(int $pregFlags): void {}
 }
 
 class RecursiveRegexIterator extends RegexIterator implements RecursiveIterator
 {
     public function __construct(RecursiveIterator $iterator, string $pattern, int $mode = RecursiveRegexIterator::MATCH, int $flags = 0, int $pregFlags = 0) {}
 
-    /** @return bool */
-    public function accept() {}
+    /** @tentative-return-type */
+    public function accept(): bool {}
 
     /**
-     * @return bool
+     * @tentative-return-type
      * @implementation-alias RecursiveFilterIterator::hasChildren
      */
-    public function hasChildren() {}
+    public function hasChildren(): bool {}
 
-    /** @return RecursiveRegexIterator */
-    public function getChildren() {}
+    /** @tentative-return-type */
+    public function getChildren(): RecursiveRegexIterator {}
 }
 
 class RecursiveTreeIterator extends RecursiveIteratorIterator
@@ -376,24 +376,24 @@ public function __construct(
         int $mode = RecursiveTreeIterator::SELF_FIRST
     ) {}
 
-    /** @return mixed */
-    public function key() {}
+    /** @tentative-return-type */
+    public function key(): mixed {}
 
-    /** @return mixed */
-    public function current() {}
+    /** @tentative-return-type */
+    public function current(): mixed {}
 
-    /** @return string */
-    public function getPrefix() {}
+    /** @tentative-return-type */
+    public function getPrefix(): string {}
 
-    /** @return void */
-    public function setPostfix(string $postfix) {}
+    /** @tentative-return-type */
+    public function setPostfix(string $postfix): void {}
 
-    /** @return void */
-    public function setPrefixPart(int $part, string $value) {}
+    /** @tentative-return-type */
+    public function setPrefixPart(int $part, string $value): void {}
 
-    /** @return string */
-    public function getEntry() {}
+    /** @tentative-return-type */
+    public function getEntry(): string {}
 
-    /** @return string */
-    public function getPostfix() {}
+    /** @tentative-return-type */
+    public function getPostfix(): string {}
 }
diff --git a/ext/spl/spl_iterators_arginfo.h b/ext/spl/spl_iterators_arginfo.h
index fbda9c21ddb85..f1621937efa00 100644
--- a/ext/spl/spl_iterators_arginfo.h
+++ b/ext/spl/spl_iterators_arginfo.h
@@ -1,36 +1,40 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: e2b69f8f12c782da28c95f16e04483bd6588e6ab */
+ * Stub hash: 889a6eed2d62fbb6af168146840189d37765dbaa */
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_EmptyIterator_current, 0, 0, 0)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_EmptyIterator_current, 0, 0, never, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_EmptyIterator_next arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_EmptyIterator_next, 0, 0, IS_VOID, 0)
+ZEND_END_ARG_INFO()
 
 #define arginfo_class_EmptyIterator_key arginfo_class_EmptyIterator_current
 
-#define arginfo_class_EmptyIterator_valid arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_EmptyIterator_valid, 0, 0, _IS_BOOL, 0)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_EmptyIterator_rewind arginfo_class_EmptyIterator_current
+#define arginfo_class_EmptyIterator_rewind arginfo_class_EmptyIterator_next
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_CallbackFilterIterator___construct, 0, 0, 2)
 	ZEND_ARG_OBJ_INFO(0, iterator, Iterator, 0)
 	ZEND_ARG_TYPE_INFO(0, callback, IS_CALLABLE, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_CallbackFilterIterator_accept arginfo_class_EmptyIterator_current
+#define arginfo_class_CallbackFilterIterator_accept arginfo_class_EmptyIterator_valid
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveCallbackFilterIterator___construct, 0, 0, 2)
 	ZEND_ARG_OBJ_INFO(0, iterator, RecursiveIterator, 0)
 	ZEND_ARG_TYPE_INFO(0, callback, IS_CALLABLE, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveCallbackFilterIterator_hasChildren arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveCallbackFilterIterator_hasChildren arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_RecursiveCallbackFilterIterator_getChildren arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_RecursiveCallbackFilterIterator_getChildren, 0, 0, RecursiveCallbackFilterIterator, 0)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveIterator_hasChildren arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIterator_hasChildren arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_RecursiveIterator_getChildren arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_RecursiveIterator_getChildren, 0, 0, RecursiveIterator, 1)
+ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveIteratorIterator___construct, 0, 0, 1)
 	ZEND_ARG_OBJ_INFO(0, iterator, Traversable, 0)
@@ -38,86 +42,92 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveIteratorIterator___construct, 0, 0
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, flags, IS_LONG, 0, "0")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveIteratorIterator_rewind arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_rewind arginfo_class_EmptyIterator_next
 
-#define arginfo_class_RecursiveIteratorIterator_valid arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_valid arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_RecursiveIteratorIterator_key arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_RecursiveIteratorIterator_key, 0, 0, IS_MIXED, 0)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveIteratorIterator_current arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_current arginfo_class_RecursiveIteratorIterator_key
 
-#define arginfo_class_RecursiveIteratorIterator_next arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_next arginfo_class_EmptyIterator_next
 
-#define arginfo_class_RecursiveIteratorIterator_getDepth arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_RecursiveIteratorIterator_getDepth, 0, 0, IS_LONG, 0)
+ZEND_END_ARG_INFO()
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveIteratorIterator_getSubIterator, 0, 0, 0)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_RecursiveIteratorIterator_getSubIterator, 0, 0, RecursiveIterator, 1)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, level, IS_LONG, 1, "null")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveIteratorIterator_getInnerIterator arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_RecursiveIteratorIterator_getInnerIterator, 0, 0, RecursiveIterator, 0)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveIteratorIterator_beginIteration arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_beginIteration arginfo_class_EmptyIterator_next
 
-#define arginfo_class_RecursiveIteratorIterator_endIteration arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_endIteration arginfo_class_EmptyIterator_next
 
-#define arginfo_class_RecursiveIteratorIterator_callHasChildren arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_callHasChildren arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_RecursiveIteratorIterator_callGetChildren arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_callGetChildren arginfo_class_RecursiveIterator_getChildren
 
-#define arginfo_class_RecursiveIteratorIterator_beginChildren arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_beginChildren arginfo_class_EmptyIterator_next
 
-#define arginfo_class_RecursiveIteratorIterator_endChildren arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_endChildren arginfo_class_EmptyIterator_next
 
-#define arginfo_class_RecursiveIteratorIterator_nextElement arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveIteratorIterator_nextElement arginfo_class_EmptyIterator_next
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveIteratorIterator_setMaxDepth, 0, 0, 0)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_RecursiveIteratorIterator_setMaxDepth, 0, 0, IS_VOID, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, maxDepth, IS_LONG, 0, "-1")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveIteratorIterator_getMaxDepth arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_MASK_EX(arginfo_class_RecursiveIteratorIterator_getMaxDepth, 0, 0, MAY_BE_LONG|MAY_BE_FALSE)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_OuterIterator_getInnerIterator arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_OuterIterator_getInnerIterator, 0, 0, Iterator, 1)
+ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_IteratorIterator___construct, 0, 0, 1)
 	ZEND_ARG_OBJ_INFO(0, iterator, Traversable, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, class, IS_STRING, 1, "null")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_IteratorIterator_getInnerIterator arginfo_class_EmptyIterator_current
+#define arginfo_class_IteratorIterator_getInnerIterator arginfo_class_OuterIterator_getInnerIterator
 
-#define arginfo_class_IteratorIterator_rewind arginfo_class_EmptyIterator_current
+#define arginfo_class_IteratorIterator_rewind arginfo_class_EmptyIterator_next
 
-#define arginfo_class_IteratorIterator_valid arginfo_class_EmptyIterator_current
+#define arginfo_class_IteratorIterator_valid arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_IteratorIterator_key arginfo_class_EmptyIterator_current
+#define arginfo_class_IteratorIterator_key arginfo_class_RecursiveIteratorIterator_key
 
-#define arginfo_class_IteratorIterator_current arginfo_class_EmptyIterator_current
+#define arginfo_class_IteratorIterator_current arginfo_class_RecursiveIteratorIterator_key
 
-#define arginfo_class_IteratorIterator_next arginfo_class_EmptyIterator_current
+#define arginfo_class_IteratorIterator_next arginfo_class_EmptyIterator_next
 
-#define arginfo_class_FilterIterator_accept arginfo_class_EmptyIterator_current
+#define arginfo_class_FilterIterator_accept arginfo_class_EmptyIterator_valid
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_FilterIterator___construct, 0, 0, 1)
 	ZEND_ARG_OBJ_INFO(0, iterator, Iterator, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_FilterIterator_rewind arginfo_class_EmptyIterator_current
+#define arginfo_class_FilterIterator_rewind arginfo_class_EmptyIterator_next
 
-#define arginfo_class_FilterIterator_next arginfo_class_EmptyIterator_current
+#define arginfo_class_FilterIterator_next arginfo_class_EmptyIterator_next
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveFilterIterator___construct, 0, 0, 1)
 	ZEND_ARG_OBJ_INFO(0, iterator, RecursiveIterator, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveFilterIterator_hasChildren arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveFilterIterator_hasChildren arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_RecursiveFilterIterator_getChildren arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_RecursiveFilterIterator_getChildren, 0, 0, RecursiveFilterIterator, 1)
+ZEND_END_ARG_INFO()
 
 #define arginfo_class_ParentIterator___construct arginfo_class_RecursiveFilterIterator___construct
 
-#define arginfo_class_ParentIterator_accept arginfo_class_EmptyIterator_current
+#define arginfo_class_ParentIterator_accept arginfo_class_EmptyIterator_valid
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_SeekableIterator_seek, 0, 0, 1)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_SeekableIterator_seek, 0, 1, IS_VOID, 0)
 	ZEND_ARG_TYPE_INFO(0, offset, IS_LONG, 0)
 ZEND_END_ARG_INFO()
 
@@ -127,95 +137,108 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo_class_LimitIterator___construct, 0, 0, 1)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, limit, IS_LONG, 0, "-1")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_LimitIterator_rewind arginfo_class_EmptyIterator_current
+#define arginfo_class_LimitIterator_rewind arginfo_class_EmptyIterator_next
 
-#define arginfo_class_LimitIterator_valid arginfo_class_EmptyIterator_current
+#define arginfo_class_LimitIterator_valid arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_LimitIterator_next arginfo_class_EmptyIterator_current
+#define arginfo_class_LimitIterator_next arginfo_class_EmptyIterator_next
 
-#define arginfo_class_LimitIterator_seek arginfo_class_SeekableIterator_seek
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_LimitIterator_seek, 0, 1, IS_LONG, 0)
+	ZEND_ARG_TYPE_INFO(0, offset, IS_LONG, 0)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_LimitIterator_getPosition arginfo_class_EmptyIterator_current
+#define arginfo_class_LimitIterator_getPosition arginfo_class_RecursiveIteratorIterator_getDepth
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_CachingIterator___construct, 0, 0, 1)
 	ZEND_ARG_OBJ_INFO(0, iterator, Iterator, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, flags, IS_LONG, 0, "CachingIterator::CALL_TOSTRING")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_CachingIterator_rewind arginfo_class_EmptyIterator_current
+#define arginfo_class_CachingIterator_rewind arginfo_class_EmptyIterator_next
 
-#define arginfo_class_CachingIterator_valid arginfo_class_EmptyIterator_current
+#define arginfo_class_CachingIterator_valid arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_CachingIterator_next arginfo_class_EmptyIterator_current
+#define arginfo_class_CachingIterator_next arginfo_class_EmptyIterator_next
 
-#define arginfo_class_CachingIterator_hasNext arginfo_class_EmptyIterator_current
+#define arginfo_class_CachingIterator_hasNext arginfo_class_EmptyIterator_valid
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_class_CachingIterator___toString, 0, 0, IS_STRING, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_CachingIterator_getFlags arginfo_class_EmptyIterator_current
+#define arginfo_class_CachingIterator_getFlags arginfo_class_RecursiveIteratorIterator_getDepth
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_CachingIterator_setFlags, 0, 0, 1)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_CachingIterator_setFlags, 0, 1, IS_VOID, 0)
 	ZEND_ARG_TYPE_INFO(0, flags, IS_LONG, 0)
 ZEND_END_ARG_INFO()
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_CachingIterator_offsetGet, 0, 0, 1)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_CachingIterator_offsetGet, 0, 1, IS_MIXED, 0)
 	ZEND_ARG_INFO(0, key)
 ZEND_END_ARG_INFO()
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_CachingIterator_offsetSet, 0, 0, 2)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_CachingIterator_offsetSet, 0, 2, IS_VOID, 0)
 	ZEND_ARG_INFO(0, key)
 	ZEND_ARG_TYPE_INFO(0, value, IS_MIXED, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_CachingIterator_offsetUnset arginfo_class_CachingIterator_offsetGet
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_CachingIterator_offsetUnset, 0, 1, IS_VOID, 0)
+	ZEND_ARG_INFO(0, key)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_CachingIterator_offsetExists arginfo_class_CachingIterator_offsetGet
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_CachingIterator_offsetExists, 0, 1, _IS_BOOL, 0)
+	ZEND_ARG_INFO(0, key)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_CachingIterator_getCache arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_CachingIterator_getCache, 0, 0, IS_ARRAY, 0)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_CachingIterator_count arginfo_class_EmptyIterator_current
+#define arginfo_class_CachingIterator_count arginfo_class_RecursiveIteratorIterator_getDepth
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveCachingIterator___construct, 0, 0, 1)
 	ZEND_ARG_OBJ_INFO(0, iterator, Iterator, 0)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, flags, IS_LONG, 0, "RecursiveCachingIterator::CALL_TOSTRING")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveCachingIterator_hasChildren arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveCachingIterator_hasChildren arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_RecursiveCachingIterator_getChildren arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_RecursiveCachingIterator_getChildren, 0, 0, RecursiveCachingIterator, 1)
+ZEND_END_ARG_INFO()
 
 #define arginfo_class_NoRewindIterator___construct arginfo_class_FilterIterator___construct
 
-#define arginfo_class_NoRewindIterator_rewind arginfo_class_EmptyIterator_current
+#define arginfo_class_NoRewindIterator_rewind arginfo_class_EmptyIterator_next
 
-#define arginfo_class_NoRewindIterator_valid arginfo_class_EmptyIterator_current
+#define arginfo_class_NoRewindIterator_valid arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_NoRewindIterator_key arginfo_class_EmptyIterator_current
+#define arginfo_class_NoRewindIterator_key arginfo_class_RecursiveIteratorIterator_key
 
-#define arginfo_class_NoRewindIterator_current arginfo_class_EmptyIterator_current
+#define arginfo_class_NoRewindIterator_current arginfo_class_RecursiveIteratorIterator_key
 
-#define arginfo_class_NoRewindIterator_next arginfo_class_EmptyIterator_current
+#define arginfo_class_NoRewindIterator_next arginfo_class_EmptyIterator_next
 
-#define arginfo_class_AppendIterator___construct arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_INFO_EX(arginfo_class_AppendIterator___construct, 0, 0, 0)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_AppendIterator_append arginfo_class_FilterIterator___construct
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_AppendIterator_append, 0, 1, IS_VOID, 0)
+	ZEND_ARG_OBJ_INFO(0, iterator, Iterator, 0)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_AppendIterator_rewind arginfo_class_EmptyIterator_current
+#define arginfo_class_AppendIterator_rewind arginfo_class_EmptyIterator_next
 
-#define arginfo_class_AppendIterator_valid arginfo_class_EmptyIterator_current
+#define arginfo_class_AppendIterator_valid arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_AppendIterator_current arginfo_class_EmptyIterator_current
+#define arginfo_class_AppendIterator_current arginfo_class_RecursiveIteratorIterator_key
 
-#define arginfo_class_AppendIterator_next arginfo_class_EmptyIterator_current
+#define arginfo_class_AppendIterator_next arginfo_class_EmptyIterator_next
 
-#define arginfo_class_AppendIterator_getIteratorIndex arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_AppendIterator_getIteratorIndex, 0, 0, IS_LONG, 1)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_AppendIterator_getArrayIterator arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_AppendIterator_getArrayIterator, 0, 0, ArrayIterator, 0)
+ZEND_END_ARG_INFO()
 
 #define arginfo_class_InfiniteIterator___construct arginfo_class_FilterIterator___construct
 
-#define arginfo_class_InfiniteIterator_next arginfo_class_EmptyIterator_current
+#define arginfo_class_InfiniteIterator_next arginfo_class_EmptyIterator_next
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RegexIterator___construct, 0, 0, 2)
 	ZEND_ARG_OBJ_INFO(0, iterator, Iterator, 0)
@@ -225,23 +248,24 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RegexIterator___construct, 0, 0, 2)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, pregFlags, IS_LONG, 0, "0")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RegexIterator_accept arginfo_class_EmptyIterator_current
+#define arginfo_class_RegexIterator_accept arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_RegexIterator_getMode arginfo_class_EmptyIterator_current
+#define arginfo_class_RegexIterator_getMode arginfo_class_RecursiveIteratorIterator_getDepth
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RegexIterator_setMode, 0, 0, 1)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_RegexIterator_setMode, 0, 1, IS_VOID, 0)
 	ZEND_ARG_TYPE_INFO(0, mode, IS_LONG, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RegexIterator_getFlags arginfo_class_EmptyIterator_current
+#define arginfo_class_RegexIterator_getFlags arginfo_class_RecursiveIteratorIterator_getDepth
 
 #define arginfo_class_RegexIterator_setFlags arginfo_class_CachingIterator_setFlags
 
-#define arginfo_class_RegexIterator_getRegex arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_RegexIterator_getRegex, 0, 0, IS_STRING, 0)
+ZEND_END_ARG_INFO()
 
-#define arginfo_class_RegexIterator_getPregFlags arginfo_class_EmptyIterator_current
+#define arginfo_class_RegexIterator_getPregFlags arginfo_class_RecursiveIteratorIterator_getDepth
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RegexIterator_setPregFlags, 0, 0, 1)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_RegexIterator_setPregFlags, 0, 1, IS_VOID, 0)
 	ZEND_ARG_TYPE_INFO(0, pregFlags, IS_LONG, 0)
 ZEND_END_ARG_INFO()
 
@@ -253,11 +277,12 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveRegexIterator___construct, 0, 0, 2
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, pregFlags, IS_LONG, 0, "0")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveRegexIterator_accept arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveRegexIterator_accept arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_RecursiveRegexIterator_hasChildren arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveRegexIterator_hasChildren arginfo_class_EmptyIterator_valid
 
-#define arginfo_class_RecursiveRegexIterator_getChildren arginfo_class_EmptyIterator_current
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_OBJ_INFO_EX(arginfo_class_RecursiveRegexIterator_getChildren, 0, 0, RecursiveRegexIterator, 0)
+ZEND_END_ARG_INFO()
 
 ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveTreeIterator___construct, 0, 0, 1)
 	ZEND_ARG_INFO(0, iterator)
@@ -266,24 +291,24 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveTreeIterator___construct, 0, 0, 1)
 	ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(0, mode, IS_LONG, 0, "RecursiveTreeIterator::SELF_FIRST")
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveTreeIterator_key arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveTreeIterator_key arginfo_class_RecursiveIteratorIterator_key
 
-#define arginfo_class_RecursiveTreeIterator_current arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveTreeIterator_current arginfo_class_RecursiveIteratorIterator_key
 
-#define arginfo_class_RecursiveTreeIterator_getPrefix arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveTreeIterator_getPrefix arginfo_class_RegexIterator_getRegex
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveTreeIterator_setPostfix, 0, 0, 1)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_RecursiveTreeIterator_setPostfix, 0, 1, IS_VOID, 0)
 	ZEND_ARG_TYPE_INFO(0, postfix, IS_STRING, 0)
 ZEND_END_ARG_INFO()
 
-ZEND_BEGIN_ARG_INFO_EX(arginfo_class_RecursiveTreeIterator_setPrefixPart, 0, 0, 2)
+ZEND_BEGIN_ARG_WITH_TENTATIVE_RETURN_TYPE_INFO_EX(arginfo_class_RecursiveTreeIterator_setPrefixPart, 0, 2, IS_VOID, 0)
 	ZEND_ARG_TYPE_INFO(0, part, IS_LONG, 0)
 	ZEND_ARG_TYPE_INFO(0, value, IS_STRING, 0)
 ZEND_END_ARG_INFO()
 
-#define arginfo_class_RecursiveTreeIterator_getEntry arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveTreeIterator_getEntry arginfo_class_RegexIterator_getRegex
 
-#define arginfo_class_RecursiveTreeIterator_getPostfix arginfo_class_EmptyIterator_current
+#define arginfo_class_RecursiveTreeIterator_getPostfix arginfo_class_RegexIterator_getRegex
 
 
 ZEND_METHOD(EmptyIterator, current);
diff --git a/ext/spl/tests/array_005.phpt b/ext/spl/tests/array_005.phpt
index cae8f422a785f..66f0f16f02f74 100644
--- a/ext/spl/tests/array_005.phpt
+++ b/ext/spl/tests/array_005.phpt
@@ -35,7 +35,7 @@ class StudentIdFilter extends FilterIterator
         $this->id = $other->getId();
     }
 
-    public function accept()
+    public function accept(): bool
     {
         echo "ACCEPT ".$this->current()->getId()." == ".$this->id."\n";
         return $this->current()->getId() == $this->id;
diff --git a/ext/spl/tests/array_009a.phpt b/ext/spl/tests/array_009a.phpt
index f8428810dbf85..b0b58e33e89ad 100644
--- a/ext/spl/tests/array_009a.phpt
+++ b/ext/spl/tests/array_009a.phpt
@@ -10,7 +10,7 @@ class MyRecursiveArrayIterator extends ArrayIterator implements RecursiveIterato
         return is_array($this->current());
     }
 
-    function getChildren()
+    function getChildren(): MyRecursiveArrayIterator
     {
         return new MyRecursiveArrayIterator($this->current());
     }
diff --git a/ext/spl/tests/bug37457.phpt b/ext/spl/tests/bug37457.phpt
index c8ee4df89702a..e8c7d7b9afca8 100644
--- a/ext/spl/tests/bug37457.phpt
+++ b/ext/spl/tests/bug37457.phpt
@@ -13,25 +13,25 @@ class Collection implements Iterator
         $this->array = $a;
     }
 
-    public function current()
+    public function current(): mixed
     {
         echo __METHOD__ . "\n";
         return current($this->array);
     }
 
-    public function key()
+    public function key(): mixed
     {
         echo __METHOD__ . "\n";
         return key($this->array);
     }
 
-    public function next()
+    public function next(): void
     {
         echo __METHOD__ . "\n";
         $this->valid = (false !== next($this->array));
     }
 
-    public function valid()
+    public function valid(): bool
     {
         echo __METHOD__ . "\n";
         return $this->valid;
@@ -46,7 +46,7 @@ class Collection implements Iterator
 
 class TestFilter extends FilterIterator
 {
-    public function accept()
+    public function accept(): bool
     {
         echo __METHOD__ . "\n";
         throw new Exception("Failure in Accept");
diff --git a/ext/spl/tests/bug42703.phpt b/ext/spl/tests/bug42703.phpt
index af2b1b8459585..d869fef0d58b0 100644
--- a/ext/spl/tests/bug42703.phpt
+++ b/ext/spl/tests/bug42703.phpt
@@ -6,18 +6,18 @@ class BlaIterator implements Iterator
 {
     public function rewind(): void { }
 
-    public function next() { }
+    public function next(): void { }
 
-    public function valid() {
+    public function valid(): bool {
         return true;
     }
 
-    public function current()
+    public function current(): mixed
     {
       throw new Exception('boo');
     }
 
-    public function key() { }
+    public function key(): mixed { return null; }
 }
 
 $it = new BlaIterator();
diff --git a/ext/spl/tests/bug54384.phpt b/ext/spl/tests/bug54384.phpt
index fa02e372f524d..6b33590e5b220 100644
--- a/ext/spl/tests/bug54384.phpt
+++ b/ext/spl/tests/bug54384.phpt
@@ -24,7 +24,7 @@ test( function() {
 echo "FilterIterator... ";
 class FilterIteratorTest extends FilterIterator {
     function __construct(){}
-    function accept(){}
+    function accept(): bool {}
 }
 test( function() {
     $o = new FilterIteratorTest;
@@ -34,7 +34,7 @@ test( function() {
 echo "RecursiveFilterIterator... ";
 class RecursiveFilterIteratorTest extends RecursiveFilterIterator {
     function __construct(){}
-    function accept(){}
+    function accept(): bool {}
 }
 test( function() {
 $o = new RecursiveFilterIteratorTest;
diff --git a/ext/spl/tests/bug69970.phpt b/ext/spl/tests/bug69970.phpt
index 6f179a230b7d9..75ae8bf0d81a6 100644
--- a/ext/spl/tests/bug69970.phpt
+++ b/ext/spl/tests/bug69970.phpt
@@ -9,7 +9,7 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator {
   function rewind(): void {
     echo "dummy\n";
   }
-  function endChildren() {
+  function endChildren(): void {
       global $count;
       echo $this->getDepth();
       if (--$count > 0) {
diff --git a/ext/spl/tests/bug73423.phpt b/ext/spl/tests/bug73423.phpt
index e1fc312651a42..2e00b328d7083 100644
--- a/ext/spl/tests/bug73423.phpt
+++ b/ext/spl/tests/bug73423.phpt
@@ -7,39 +7,39 @@ class foo implements \RecursiveIterator
   {
     public $foo = [];
 
-    public Function current ()
+    public Function current(): mixed
       {
         return current ($this->foo);
       }
 
-    public Function key ()
+    public Function key(): mixed
       {
         return key ($this->foo);
       }
 
-    public Function next ()
+    public Function next(): void
       {
         next ($this->foo);
       }
 
-    public Function rewind ()
+    public Function rewind(): void
       {
         reset ($this->foo);
       }
 
-    public Function valid ()
+    public Function valid(): bool
       {
         return current ($this->foo) !== false;
       }
 
-    public Function getChildren ()
+    public Function getChildren(): ?RecursiveIterator
       {
         return current ($this->foo);
       }
 
-    public Function hasChildren ()
+    public Function hasChildren(): bool
       {
-        return (bool) count ($this->foo);
+        return (bool) count($this->foo);
       }
   }
 
@@ -53,7 +53,7 @@ class fooIterator extends \RecursiveFilterIterator
         /* CRASH */
       }
 
-    public Function accept ()
+    public Function accept(): bool
       {
         return true;
       }
diff --git a/ext/spl/tests/bug74669.phpt b/ext/spl/tests/bug74669.phpt
index e942d2c5f0761..0966a4cf27e15 100644
--- a/ext/spl/tests/bug74669.phpt
+++ b/ext/spl/tests/bug74669.phpt
@@ -19,22 +19,22 @@ class Container implements Iterator
         $this->container->append($element);
     }
 
-    public function current()
+    public function current(): mixed
     {
         return $this->iterator->current();
     }
 
-    public function next()
+    public function next(): void
     {
         $this->iterator->next();
     }
 
-    public function key()
+    public function key(): mixed
     {
         return $this->iterator->key();
     }
 
-    public function valid()
+    public function valid(): bool
     {
         return $this->iterator->valid();
     }
diff --git a/ext/spl/tests/bug77263.phpt b/ext/spl/tests/bug77263.phpt
index ddd5fba3cd499..386744793a9cb 100644
--- a/ext/spl/tests/bug77263.phpt
+++ b/ext/spl/tests/bug77263.phpt
@@ -9,11 +9,11 @@ touch("$dir/file1");
 touch("$dir/subdir/file2");
 
 class Filter1 extends RecursiveFilterIterator {
-    public function accept() { return $this->getInnerIterator()->getSubPathname() != ''; }
+    public function accept(): bool { return $this->getInnerIterator()->getSubPathname() != ''; }
 }
 
 class Filter2 extends RecursiveFilterIterator {
-    public function accept() { return $this->getInnerIterator()->getSubPathname() != ' '; }
+    public function accept(): bool { return $this->getInnerIterator()->getSubPathname() != ' '; }
 }
 
 $iterator = new RecursiveDirectoryIterator($dir, FilesystemIterator::SKIP_DOTS );
diff --git a/ext/spl/tests/iterator_001.phpt b/ext/spl/tests/iterator_001.phpt
index 2517e0b566140..6912aa5643e12 100644
--- a/ext/spl/tests/iterator_001.phpt
+++ b/ext/spl/tests/iterator_001.phpt
@@ -20,26 +20,26 @@ class NumericArrayIterator implements Iterator
         $this->i = 0;
     }
 
-    public function valid()
+    public function valid(): bool
     {
         $ret = $this->i < count($this->a);
         echo __METHOD__ . '(' . ($ret ? 'true' : 'false') . ")\n";
         return $ret;
     }
 
-    public function key()
+    public function key(): mixed
     {
         echo __METHOD__ . "\n";
         return $this->i;
     }
 
-    public function current()
+    public function current(): mixed
     {
         echo __METHOD__ . "\n";
         return $this->a[$this->i];
     }
 
-    public function next()
+    public function next(): void
     {
         echo __METHOD__ . "\n";
         $this->i++;
@@ -54,7 +54,7 @@ class NumericArrayIterator implements Iterator
 
 class SeekableNumericArrayIterator extends NumericArrayIterator implements SeekableIterator
 {
-    public function seek($index)
+    public function seek($index): void
     {
         if ($index < count($this->a)) {
             $this->i = $index;
diff --git a/ext/spl/tests/iterator_003.phpt b/ext/spl/tests/iterator_003.phpt
index b7b331a496d5a..dfb44b94f9b5d 100644
--- a/ext/spl/tests/iterator_003.phpt
+++ b/ext/spl/tests/iterator_003.phpt
@@ -35,7 +35,7 @@ class StudentIdFilter extends FilterIterator
         $this->id = $other->getId();
     }
 
-    public function accept()
+    public function accept(): bool
     {
         echo "ACCEPT ".$this->current()->getId()." == ".$this->id."\n";
         return $this->current()->getId() == $this->id;
diff --git a/ext/spl/tests/iterator_004.phpt b/ext/spl/tests/iterator_004.phpt
index bb849580308d7..bc23ed35475c5 100644
--- a/ext/spl/tests/iterator_004.phpt
+++ b/ext/spl/tests/iterator_004.phpt
@@ -20,26 +20,26 @@ class NumericArrayIterator implements Iterator
         $this->i = 0;
     }
 
-    public function valid()
+    public function valid(): bool
     {
         $ret = $this->i < count($this->a);
         echo __METHOD__ . '(' . ($ret ? 'true' : 'false') . ")\n";
         return $ret;
     }
 
-    public function key()
+    public function key(): mixed
     {
         echo __METHOD__ . "\n";
         return $this->i;
     }
 
-    public function current()
+    public function current(): mixed
     {
         echo __METHOD__ . "\n";
         return $this->a[$this->i];
     }
 
-    public function next()
+    public function next(): void
     {
         echo __METHOD__ . "\n";
         $this->i++;
@@ -48,7 +48,7 @@ class NumericArrayIterator implements Iterator
 
 class SeekableNumericArrayIterator extends NumericArrayIterator implements SeekableIterator
 {
-    public function seek($index)
+    public function seek($index): void
     {
         if ($index < count($this->a)) {
             $this->i = $index;
diff --git a/ext/spl/tests/iterator_007.phpt b/ext/spl/tests/iterator_007.phpt
index 9ad087da367d0..f1cb11229d65d 100644
--- a/ext/spl/tests/iterator_007.phpt
+++ b/ext/spl/tests/iterator_007.phpt
@@ -39,22 +39,22 @@ class NoRewindIteratorEx extends NoRewindIterator
         echo __METHOD__ . "\n";
         parent::rewind();
     }
-    function valid()
+    function valid(): bool
     {
         echo __METHOD__ . "\n";
         return parent::valid();
     }
-    function current()
+    function current(): mixed
     {
         echo __METHOD__ . "\n";
         return parent::current();
     }
-    function key()
+    function key(): mixed
     {
         echo __METHOD__ . "\n";
         return parent::key();
     }
-    function next()
+    function next(): void
     {
         echo __METHOD__ . "\n";
         parent::next();
diff --git a/ext/spl/tests/iterator_009.phpt b/ext/spl/tests/iterator_009.phpt
index 19447deac458e..bd8eb99c4d0db 100644
--- a/ext/spl/tests/iterator_009.phpt
+++ b/ext/spl/tests/iterator_009.phpt
@@ -5,27 +5,27 @@ SPL: EmptyIterator
 
 class EmptyIteratorEx extends EmptyIterator
 {
-    function rewind()
+    function rewind(): void
     {
         echo __METHOD__ . "\n";
         parent::rewind();
     }
-    function valid()
+    function valid(): bool
     {
         echo __METHOD__ . "\n";
         return parent::valid();
     }
-    function current()
+    function current(): never
     {
         echo __METHOD__ . "\n";
-        return parent::current();
+        parent::current();
     }
-    function key()
+    function key(): never
     {
         echo __METHOD__ . "\n";
-        return parent::key();
+        parent::key();
     }
-    function next()
+    function next(): void
     {
         echo __METHOD__ . "\n";
         parent::next();
diff --git a/ext/spl/tests/iterator_014.phpt b/ext/spl/tests/iterator_014.phpt
index 5e15854ad10e9..d68a968954b40 100644
--- a/ext/spl/tests/iterator_014.phpt
+++ b/ext/spl/tests/iterator_014.phpt
@@ -27,42 +27,42 @@ class MyRecursiveArrayIterator extends RecursiveArrayIterator
 
 class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
 {
-    function rewind()
+    function rewind(): void
     {
         echo __METHOD__ . "\n";
         parent::rewind();
     }
 
-    function valid()
+    function valid(): bool
     {
         echo __METHOD__ . "\n";
         return parent::valid();
     }
 
-    function current()
+    function current(): mixed
     {
         echo __METHOD__ . "\n";
         return parent::current();
     }
 
-    function key()
+    function key(): mixed
     {
         echo __METHOD__ . "\n";
         return parent::key();
     }
 
-    function next()
+    function next(): void
     {
         echo __METHOD__ . "\n";
         parent::next();
     }
 
-    function beginChildren()
+    function beginChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
     }
 
-    function endChildren()
+    function endChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
     }
diff --git a/ext/spl/tests/iterator_015.phpt b/ext/spl/tests/iterator_015.phpt
index f83366bb1c43d..6237533a58db0 100644
--- a/ext/spl/tests/iterator_015.phpt
+++ b/ext/spl/tests/iterator_015.phpt
@@ -5,21 +5,21 @@ SPL: RecursiveIteratorIterator and beginChildren/endChildren
 
 class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
 {
-    function rewind()
+    function rewind(): void
     {
         echo "<ul>\n";
         parent::rewind();
     }
-    function beginChildren()
+    function beginChildren(): void
     {
         echo str_repeat('  ',$this->getDepth())."<ul>\n";
     }
 
-    function endChildren()
+    function endChildren(): void
     {
         echo str_repeat('  ',$this->getDepth())."</ul>\n";
     }
-    function valid()
+    function valid(): bool
     {
         if (!parent::valid()) {
             echo "<ul>\n";
diff --git a/ext/spl/tests/iterator_016.phpt b/ext/spl/tests/iterator_016.phpt
index 90a89ceff806f..abc81c165ae66 100644
--- a/ext/spl/tests/iterator_016.phpt
+++ b/ext/spl/tests/iterator_016.phpt
@@ -18,21 +18,21 @@ class MenuOutput extends RecursiveIteratorIterator
     {
         parent::__construct($it);
     }
-    function rewind()
+    function rewind(): void
     {
         echo "<ul>\n";
         parent::rewind();
     }
-    function beginChildren()
+    function beginChildren(): void
     {
         echo str_repeat('  ',$this->getDepth())."<ul>\n";
     }
 
-    function endChildren()
+    function endChildren(): void
     {
         echo str_repeat('  ',$this->getDepth())."</ul>\n";
     }
-    function valid()
+    function valid(): bool
     {
         if (!parent::valid()) {
             echo "<ul>\n";
diff --git a/ext/spl/tests/iterator_021.phpt b/ext/spl/tests/iterator_021.phpt
index e495a5aaf3403..a99ab9cbbf2e5 100644
--- a/ext/spl/tests/iterator_021.phpt
+++ b/ext/spl/tests/iterator_021.phpt
@@ -37,14 +37,14 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         parent::__construct($it);
     }
 
-    function rewind()
+    function rewind(): void
     {
         echo __METHOD__ . "\n";
         $this->skip = false;
         parent::rewind();
     }
 
-    function valid()
+    function valid(): bool
     {
         echo __METHOD__ . "\n";
         if ($this->skip)
@@ -55,25 +55,25 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         return parent::valid();
     }
 
-    function current()
+    function current(): mixed
     {
         echo __METHOD__ . "\n";
         return parent::current();
     }
 
-    function key()
+    function key(): mixed
     {
         echo __METHOD__ . "\n";
         return parent::key();
     }
 
-    function next()
+    function next(): void
     {
         echo __METHOD__ . "\n";
         parent::next();
     }
 
-    function callHasChildren()
+    function callHasChildren(): bool
     {
         $this->skip = false;
         $has = parent::callHasChildren();
@@ -89,12 +89,12 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         return $res;
     }
 
-    function beginChildren()
+    function beginChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
     }
 
-    function endChildren()
+    function endChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
     }
diff --git a/ext/spl/tests/iterator_022.phpt b/ext/spl/tests/iterator_022.phpt
index 5a6829fa0bb37..fda42a97c830b 100644
--- a/ext/spl/tests/iterator_022.phpt
+++ b/ext/spl/tests/iterator_022.phpt
@@ -37,7 +37,7 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         parent::__construct($it);
     }
 
-    function rewind()
+    function rewind(): void
     {
         echo __METHOD__ . "\n";
         $this->skip = false;
@@ -55,25 +55,25 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         return parent::valid();
     }
 
-    function current()
+    function current(): mixed
     {
         echo __METHOD__ . "\n";
         return parent::current();
     }
 
-    function key()
+    function key(): int
     {
         echo __METHOD__ . "\n";
         return parent::key();
     }
 
-    function next()
+    function next(): void
     {
         echo __METHOD__ . "\n";
         parent::next();
     }
 
-    function callHasChildren()
+    function callHasChildren(): bool
     {
         $this->skip = false;
         $has = parent::callHasChildren();
@@ -89,7 +89,7 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         return $res;
     }
 
-    function callGetChildren()
+    function callGetChildren(): ?MyRecursiveArrayIterator
     {
         if ($this->over == 2)
         {
@@ -100,12 +100,12 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         return new MyRecursiveArrayIterator($this->current());
     }
 
-    function beginChildren()
+    function beginChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
     }
 
-    function endChildren()
+    function endChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
     }
diff --git a/ext/spl/tests/iterator_023.phpt b/ext/spl/tests/iterator_023.phpt
index 780a7c2c15b72..8c7121ff2cb51 100644
--- a/ext/spl/tests/iterator_023.phpt
+++ b/ext/spl/tests/iterator_023.phpt
@@ -37,14 +37,14 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         parent::__construct($it, RecursiveIteratorIterator::LEAVES_ONLY, RecursiveIteratorIterator::CATCH_GET_CHILD);
     }
 
-    function rewind()
+    function rewind(): void
     {
         echo __METHOD__ . "\n";
         $this->skip = false;
         parent::rewind();
     }
 
-    function valid()
+    function valid(): bool
     {
         echo __METHOD__ . "\n";
         if ($this->skip)
@@ -55,25 +55,25 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         return parent::valid();
     }
 
-    function current()
+    function current(): mixed
     {
         echo __METHOD__ . "\n";
         return parent::current();
     }
 
-    function key()
+    function key(): int
     {
         echo __METHOD__ . "\n";
         return parent::key();
     }
 
-    function next()
+    function next(): void
     {
         echo __METHOD__ . "\n";
         parent::next();
     }
 
-    function callHasChildren()
+    function callHasChildren(): bool
     {
         $this->skip = false;
         $has = parent::callHasChildren();
@@ -89,7 +89,7 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         return $res;
     }
 
-    function callGetChildren()
+    function callGetChildren(): MyRecursiveArrayIterator
     {
         if ($this->over == 2)
         {
@@ -100,12 +100,12 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         return new MyRecursiveArrayIterator($this->current());
     }
 
-    function beginChildren()
+    function beginChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
     }
 
-    function endChildren()
+    function endChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
     }
diff --git a/ext/spl/tests/iterator_025.phpt b/ext/spl/tests/iterator_025.phpt
index f3df902a6461e..d8d1489a0caf6 100644
--- a/ext/spl/tests/iterator_025.phpt
+++ b/ext/spl/tests/iterator_025.phpt
@@ -5,12 +5,12 @@ SPL: RecursiveIteratorIterator and begin/endIteration()
 
 class MyRecursiveIteratorIterator extends RecursiveIteratorIterator
 {
-    function beginIteration()
+    function beginIteration(): void
     {
         echo __METHOD__ . "()\n";
     }
 
-    function endIteration()
+    function endIteration(): void
     {
         echo __METHOD__ . "()\n";
     }
diff --git a/ext/spl/tests/iterator_031.phpt b/ext/spl/tests/iterator_031.phpt
index 249aec2aef962..610e056f53801 100644
--- a/ext/spl/tests/iterator_031.phpt
+++ b/ext/spl/tests/iterator_031.phpt
@@ -26,19 +26,19 @@ class MyAppendIterator extends AppendIterator
         echo __METHOD__ . "\n";
     }
 
-    function rewind()
+    function rewind(): void
     {
         echo __METHOD__ . "\n";
         parent::rewind();
     }
 
-    function valid()
+    function valid(): bool
     {
         echo __METHOD__ . "\n";
         return parent::valid();
     }
 
-    function append(Iterator $what)
+    function append(Iterator $what): void
     {
         echo __METHOD__ . "\n";
         parent::append($what);
diff --git a/ext/spl/tests/iterator_034.phpt b/ext/spl/tests/iterator_034.phpt
index df1488e4b4835..b3993c6245d6c 100644
--- a/ext/spl/tests/iterator_034.phpt
+++ b/ext/spl/tests/iterator_034.phpt
@@ -42,38 +42,38 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         parent::__construct($it);
     }
 
-    function rewind()
+    function rewind(): void
     {
         echo __METHOD__ . "() - BEGIN\n";
         parent::rewind();
         echo __METHOD__ . "() - DONE\n";
     }
 
-    function valid()
+    function valid(): bool
     {
         echo __METHOD__ . "()\n";
         return parent::valid();
     }
 
-    function current()
+    function current(): mixed
     {
         echo __METHOD__ . "()\n";
         return parent::current();
     }
 
-    function key()
+    function key(): int
     {
         echo __METHOD__ . "()\n";
         return parent::key();
     }
 
-    function next()
+    function next(): void
     {
         echo __METHOD__ . "()\n";
         parent::next();
     }
 
-    function callHasChildren()
+    function callHasChildren(): bool
     {
         $has = parent::callHasChildren();
         $res = $this->getDepth() < $this->max_depth && $has;
@@ -81,13 +81,13 @@ class RecursiveArrayIteratorIterator extends RecursiveIteratorIterator
         return $res;
     }
 
-    function beginChildren()
+    function beginChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
         parent::beginChildren();
     }
 
-    function endChildren()
+    function endChildren(): void
     {
         echo __METHOD__ . "(".$this->getDepth().")\n";
         parent::endChildren();
diff --git a/ext/spl/tests/iterator_039.phpt b/ext/spl/tests/iterator_039.phpt
index 18f9a24168fa2..32ddc077e2216 100644
--- a/ext/spl/tests/iterator_039.phpt
+++ b/ext/spl/tests/iterator_039.phpt
@@ -14,31 +14,31 @@ class NumericArrayIterator implements Iterator
         $this->a = $a;
     }
 
-    public function valid()
+    public function valid(): bool
     {
         echo __METHOD__ . "\n";
         return $this->i < count($this->a);
     }
 
-    public function rewind()
+    public function rewind(): void
     {
         echo __METHOD__ . "\n";
         $this->i = 0;
     }
 
-    public function key()
+    public function key(): mixed
     {
         echo __METHOD__ . "\n";
         return $this->i;
     }
 
-    public function current()
+    public function current(): mixed
     {
         echo __METHOD__ . "\n";
         return $this->a[$this->i];
     }
 
-    public function next()
+    public function next(): void
     {
         echo __METHOD__ . "\n";
         $this->i++;
diff --git a/ext/spl/tests/iterator_040.phpt b/ext/spl/tests/iterator_040.phpt
index 1e8bd55764545..834276d45733e 100644
--- a/ext/spl/tests/iterator_040.phpt
+++ b/ext/spl/tests/iterator_040.phpt
@@ -5,7 +5,7 @@ SPL: RecursiveFilterIterator
 
 class MyRecursiveFilterIterator extends RecursiveFilterIterator
 {
-    function accept()
+    function accept(): bool
     {
         return true;
     }
diff --git a/ext/spl/tests/iterator_052.phpt b/ext/spl/tests/iterator_052.phpt
index e73d40203d539..07b12601d1327 100644
--- a/ext/spl/tests/iterator_052.phpt
+++ b/ext/spl/tests/iterator_052.phpt
@@ -23,7 +23,7 @@ class MyRegexIterator extends RegexIterator
         }
     }
 
-    function accept()
+    function accept(): bool
     {
         @preg_match_all($this->re, (string)($this->uk ? $this->key() : $this->current()), $sub);
         $ret = parent::accept();
diff --git a/ext/spl/tests/iterator_053.phpt b/ext/spl/tests/iterator_053.phpt
index ac8f438a04611..64898624ce421 100644
--- a/ext/spl/tests/iterator_053.phpt
+++ b/ext/spl/tests/iterator_053.phpt
@@ -23,7 +23,7 @@ class MyRegexIterator extends RegexIterator
         }
     }
 
-    function accept()
+    function accept(): bool
     {
         @preg_match_all($this->re, (string)($this->uk ? $this->key() : $this->current()), $sub);
         $ret = parent::accept();
diff --git a/ext/spl/tests/iterator_056.phpt b/ext/spl/tests/iterator_056.phpt
index 54a31d18baf49..84427b8707dcc 100644
--- a/ext/spl/tests/iterator_056.phpt
+++ b/ext/spl/tests/iterator_056.phpt
@@ -6,7 +6,7 @@ Sebastian Schürmann
 <?php
 
 class myFilterIterator extends FilterIterator {
-    function accept() { }
+    function accept(): bool { }
 }
 
 class myCachingIterator extends CachingIterator { }
diff --git a/ext/spl/tests/iterator_058.phpt b/ext/spl/tests/iterator_058.phpt
index ebe7a1ed2c16b..451c2d107b5c0 100644
--- a/ext/spl/tests/iterator_058.phpt
+++ b/ext/spl/tests/iterator_058.phpt
@@ -6,11 +6,11 @@ Sebastian Schürmann
 <?php
 class myIterator implements Iterator {
 
-    function current() {}
-    function next() {}
-    function key() {}
-    function valid() {}
-    function rewind() {}
+    function current(): mixed {}
+    function next(): void {}
+    function key(): mixed {}
+    function valid(): bool {}
+    function rewind(): void {}
 
 }
 try {
diff --git a/ext/spl/tests/iterator_068.phpt b/ext/spl/tests/iterator_068.phpt
index 00006a3b60fab..5dfa1458a0542 100644
--- a/ext/spl/tests/iterator_068.phpt
+++ b/ext/spl/tests/iterator_068.phpt
@@ -7,11 +7,11 @@ class Test implements Iterator {
     function foo() {
         echo __METHOD__ . "()\n";
     }
-    function rewind() {}
-    function valid() {}
-    function current() {}
-    function key() {}
-    function next() {}
+    function rewind(): void {}
+    function valid(): bool {}
+    function current(): mixed {}
+    function key(): mixed {}
+    function next(): void {}
 }
 
 class TestIteratorIterator extends IteratorIterator {
diff --git a/ext/spl/tests/iterator_071.phpt b/ext/spl/tests/iterator_071.phpt
index 501771119ad76..7f525eb2c61d6 100644
--- a/ext/spl/tests/iterator_071.phpt
+++ b/ext/spl/tests/iterator_071.phpt
@@ -10,7 +10,7 @@ $recArrIt = new RecursiveArrayIterator($arrOb->getIterator());
 
 class MyRecursiveIteratorIterator extends RecursiveIteratorIterator {
 
-    function nextelement() {
+    function nextelement(): void {
         echo __METHOD__."\n";
     }
 }
diff --git a/ext/spl/tests/recursiveIteratorIterator_beginchildren_error.phpt b/ext/spl/tests/recursiveIteratorIterator_beginchildren_error.phpt
index e8b71ebb0d683..6a7d3eb8a514c 100644
--- a/ext/spl/tests/recursiveIteratorIterator_beginchildren_error.phpt
+++ b/ext/spl/tests/recursiveIteratorIterator_beginchildren_error.phpt
@@ -10,7 +10,7 @@ $recArrIt = new RecursiveArrayIterator($arrOb->getIterator());
 
 class MyRecursiveIteratorIterator extends RecursiveIteratorIterator {
 
-    function beginchildren() {
+    function beginchildren(): void {
         throw new Exception;
     }
 }
diff --git a/ext/spl/tests/recursiveIteratorIterator_callHasChildren_error.phpt b/ext/spl/tests/recursiveIteratorIterator_callHasChildren_error.phpt
index df669375251ee..1c96ee9fcd0bf 100644
--- a/ext/spl/tests/recursiveIteratorIterator_callHasChildren_error.phpt
+++ b/ext/spl/tests/recursiveIteratorIterator_callHasChildren_error.phpt
@@ -10,7 +10,7 @@ $recArrIt = new RecursiveArrayIterator($arrOb->getIterator());
 
 class MyRecursiveIteratorIterator extends RecursiveIteratorIterator {
 
-    function callHasChildren() {
+    function callHasChildren(): bool {
         throw new Exception;
     }
 }
diff --git a/ext/spl/tests/recursiveIteratorIterator_endchildren_error.phpt b/ext/spl/tests/recursiveIteratorIterator_endchildren_error.phpt
index 7bd08d444f578..7f9f9411dd98b 100644
--- a/ext/spl/tests/recursiveIteratorIterator_endchildren_error.phpt
+++ b/ext/spl/tests/recursiveIteratorIterator_endchildren_error.phpt
@@ -10,7 +10,7 @@ $recArrIt = new RecursiveArrayIterator($arrOb->getIterator());
 
 class MyRecursiveIteratorIterator extends RecursiveIteratorIterator {
 
-    function endchildren() {
+    function endchildren(): void {
         throw new Exception;
     }
 }
diff --git a/ext/spl/tests/recursiveIteratorIterator_nextelement_error.phpt b/ext/spl/tests/recursiveIteratorIterator_nextelement_error.phpt
index bd084f54e6f79..d92d309c754ba 100644
--- a/ext/spl/tests/recursiveIteratorIterator_nextelement_error.phpt
+++ b/ext/spl/tests/recursiveIteratorIterator_nextelement_error.phpt
@@ -10,7 +10,7 @@ $recArrIt = new RecursiveArrayIterator($arrOb->getIterator());
 
 class MyRecursiveIteratorIterator extends RecursiveIteratorIterator {
 
-    function nextelement() {
+    function nextelement(): void {
         throw new Exception;
     }
 }
diff --git a/ext/spl/tests/recursivecomparedualiterator.inc b/ext/spl/tests/recursivecomparedualiterator.inc
index 15f8b177c0c41..5e3546fe32997 100644
--- a/ext/spl/tests/recursivecomparedualiterator.inc
+++ b/ext/spl/tests/recursivecomparedualiterator.inc
@@ -34,7 +34,7 @@ class RecursiveCompareDualIterator extends RecursiveIteratorIterator
 
     /** Rewind iteration and comparison process. Starting with $equal = true.
      */
-    function rewind()
+    function rewind(): void
     {
         $this->equal = true;
         parent::rewind();
@@ -43,7 +43,7 @@ class RecursiveCompareDualIterator extends RecursiveIteratorIterator
     /** Calculate $equal
      * @see $equal
      */
-    function endChildren()
+    function endChildren(): void
     {
         $this->equal &= !$this->getInnerIterator()->getLHS()->valid()
                      && !$this->getInnerIterator()->getRHS()->valid();
diff --git a/ext/spl/tests/recursiveiteratoriterator_beginiteration_basic.phpt b/ext/spl/tests/recursiveiteratoriterator_beginiteration_basic.phpt
index 0eea8b28fa4b0..986d898269c51 100644
--- a/ext/spl/tests/recursiveiteratoriterator_beginiteration_basic.phpt
+++ b/ext/spl/tests/recursiveiteratoriterator_beginiteration_basic.phpt
@@ -14,7 +14,7 @@ foreach ($iterator as $element) {
 }
 
 class SkipsFirstElementRecursiveIteratorIterator extends RecursiveIteratorIterator {
-  public function beginIteration() {
+  public function beginIteration(): void {
     echo "::beginIteration() was invoked\n";
     $this->next();
   }
diff --git a/ext/spl/tests/recursiveiteratoriterator_enditeration_basic.phpt b/ext/spl/tests/recursiveiteratoriterator_enditeration_basic.phpt
index b7c3cf67023d7..000a411091440 100644
--- a/ext/spl/tests/recursiveiteratoriterator_enditeration_basic.phpt
+++ b/ext/spl/tests/recursiveiteratoriterator_enditeration_basic.phpt
@@ -14,7 +14,7 @@ foreach ($iterator as $element) {
 }
 
 class EndIterationRecursiveIteratorIterator extends RecursiveIteratorIterator {
-  public function endIteration() {
+  public function endIteration(): void {
     echo "::endIteration() was invoked\n";
   }
 }
diff --git a/ext/spl/tests/recursiveiteratoriterator_nextelement_basic.phpt b/ext/spl/tests/recursiveiteratoriterator_nextelement_basic.phpt
index b5508f73e4527..8b3a31112577f 100644
--- a/ext/spl/tests/recursiveiteratoriterator_nextelement_basic.phpt
+++ b/ext/spl/tests/recursiveiteratoriterator_nextelement_basic.phpt
@@ -14,7 +14,7 @@ foreach ($iterator as $element) {
 }
 
 class NextElementRecursiveIteratorIterator extends RecursiveIteratorIterator {
-  public function nextElement() {
+  public function nextElement(): void {
     echo "::nextElement() was invoked\n";
   }
 }