Consistent error messages for unsetting a string offset

Author: Girgias

Zend/tests/bug24773.phpt

@@ -6,7 +6,7 @@ Bug #24773 (unset() of integers treated as arrays causes a crash)
     unset($array["lvl1"]["lvl2"]["b"]);
 ?>
 --EXPECTF--
-Fatal error: Uncaught TypeError: Cannot access offset of type string in unset in %s:%d
+Fatal error: Uncaught Error: Cannot unset string offsets in %s:%d
 Stack trace:
 #0 {main}
   thrown in %s on line %d

Zend/zend.c

@@ -1728,7 +1728,12 @@ ZEND_API ZEND_COLD void zend_illegal_container_offset(const zend_string *contain
 				zend_zval_type_name(offset));
 			return;
 		case BP_VAR_UNSET:
-			zend_type_error("Cannot access offset of type %s in unset", zend_zval_type_name(offset));
+			/* Consistent error for when trying to unset a string offset */
+			if (zend_string_equals(container, ZSTR_KNOWN(ZEND_STR_STRING))) {
+				zend_throw_error(NULL, "Cannot unset string offsets");
+			} else {
+				zend_type_error("Cannot access offset of type %s in unset", zend_zval_type_name(offset));
+			}
 			return;
 		default:
 			zend_type_error("Cannot access offset of type %s on %s",