From 9e1497c758d4615482e76c05258f1b4812ef8f9d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?M=C3=A1t=C3=A9=20Kocsis?= <kocsismate@woohoolabs.com>
Date: Fri, 18 Sep 2020 22:05:41 +0200
Subject: [PATCH] Fix consistency between grapheme_substr() and substr()

---
 ext/intl/grapheme/grapheme_string.c |  4 +++-
 ext/intl/tests/grapheme_substr.phpt | 31 +++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 ext/intl/tests/grapheme_substr.phpt

diff --git a/ext/intl/grapheme/grapheme_string.c b/ext/intl/grapheme/grapheme_string.c
index 8706381e58825..3d706c851aea1 100644
--- a/ext/intl/grapheme/grapheme_string.c
+++ b/ext/intl/grapheme/grapheme_string.c
@@ -375,7 +375,9 @@ PHP_FUNCTION(grapheme_substr)
 		RETURN_THROWS();
 	}
 
-	if ( OUTSIDE_STRING(lstart, str_len)) {
+	if (str_len == 0 && lstart == 0) {
+		RETURN_EMPTY_STRING();
+	} else if (OUTSIDE_STRING(lstart, str_len)) {
 		zend_argument_value_error(2, "must be contained in argument #1 ($string)");
 		RETURN_THROWS();
 	}
diff --git a/ext/intl/tests/grapheme_substr.phpt b/ext/intl/tests/grapheme_substr.phpt
new file mode 100644
index 0000000000000..f56c18a8b2f26
--- /dev/null
+++ b/ext/intl/tests/grapheme_substr.phpt
@@ -0,0 +1,31 @@
+--TEST--
+Test grapheme_substr() function
+--SKIPIF--
+<?php if( !extension_loaded( 'intl' ) ) print 'skip'; ?>
+--FILE--
+<?php
+
+ini_set("intl.error_level", E_WARNING);
+
+var_dump(grapheme_substr("", 0, 5));
+
+try {
+    grapheme_substr("", 1, 5);
+} catch (ValueError $exception) {
+    echo $exception->getMessage() . "\n";
+}
+
+var_dump(grapheme_substr("abc", 0, 5));
+
+try {
+    grapheme_substr("abc", 3, 5);
+} catch (ValueError $exception) {
+    echo $exception->getMessage() . "\n";
+}
+
+?>
+--EXPECT--
+string(0) ""
+grapheme_substr(): Argument #2 ($start) must be contained in argument #1 ($string)
+string(3) "abc"
+grapheme_substr(): Argument #2 ($start) must be contained in argument #1 ($string)