From 66bfd180e903ae5a26160523db1d8f25bf798d2c Mon Sep 17 00:00:00 2001
From: Jorg Sowa <jorg.sowa@gmail.com>
Date: Mon, 15 Jun 2026 23:22:56 +0200
Subject: [PATCH] ext/spl: ignore leading namespace separator in spl_autoload()

Strip a leading "\\" before lowercasing, mirroring zend_lookup_class_ex(),
so both spellings resolve identically.
---
 ext/spl/php_spl.c                              |  7 ++++++-
 .../tests/spl_autoload_leading_backslash.phpt  | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 ext/spl/tests/spl_autoload_leading_backslash.phpt

diff --git a/ext/spl/php_spl.c b/ext/spl/php_spl.c
index 78315e9880b4..42fbeba71dbe 100644
--- a/ext/spl/php_spl.c
+++ b/ext/spl/php_spl.c
@@ -310,7 +310,12 @@ PHP_FUNCTION(spl_autoload)
 		pos_len = (int)ZSTR_LEN(file_exts);
 	}
 
-	lc_name = zend_string_tolower(class_name);
+	if (ZSTR_VAL(class_name)[0] == '\\') {
+		lc_name = zend_string_alloc(ZSTR_LEN(class_name) - 1, 0);
+		zend_str_tolower_copy(ZSTR_VAL(lc_name), ZSTR_VAL(class_name) + 1, ZSTR_LEN(class_name) - 1);
+	} else {
+		lc_name = zend_string_tolower(class_name);
+	}
 	while (pos && *pos && !EG(exception)) {
 		pos1 = strchr(pos, ',');
 		if (pos1) {
diff --git a/ext/spl/tests/spl_autoload_leading_backslash.phpt b/ext/spl/tests/spl_autoload_leading_backslash.phpt
new file mode 100644
index 000000000000..ff8ae3234eee
--- /dev/null
+++ b/ext/spl/tests/spl_autoload_leading_backslash.phpt
@@ -0,0 +1,18 @@
+--TEST--
+spl_autoload(): a leading "\" in the class name is ignored
+--FILE--
+<?php
+
+set_include_path(__DIR__);
+spl_autoload_extensions(".inc");
+
+spl_autoload("DualIterator");
+var_dump(class_exists("DualIterator", false));
+
+spl_autoload("\\RecursiveDualIterator");
+var_dump(class_exists("RecursiveDualIterator", false));
+
+?>
+--EXPECT--
+bool(true)
+bool(true)