From d64561787cbfe2aa5179b1e51aa27398e465a383 Mon Sep 17 00:00:00 2001
From: Artyom Osepyan <art@osepyan.ru>
Date: Fri, 21 Nov 2025 00:03:50 +0300
Subject: [PATCH 1/3] fix: use mb_strlen in substrReplace for multibyte safety

refs: https://github.com/laravel/framework/issues/57838
---
 src/Illuminate/Support/Str.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Illuminate/Support/Str.php b/src/Illuminate/Support/Str.php
index 164018788683..cccff1a75f6a 100644
--- a/src/Illuminate/Support/Str.php
+++ b/src/Illuminate/Support/Str.php
@@ -1748,7 +1748,7 @@ public static function substrCount($haystack, $needle, $offset = 0, $length = nu
     public static function substrReplace($string, $replace, $offset = 0, $length = null)
     {
         if ($length === null) {
-            $length = strlen($string);
+            $length = mb_strlen($string);
         }
 
         return substr_replace($string, $replace, $offset, $length);

From bb068a70f67f6d4fed906077407329e4649b8840 Mon Sep 17 00:00:00 2001
From: Artyom Osepyan <art@osepyan.ru>
Date: Fri, 21 Nov 2025 01:09:33 +0300
Subject: [PATCH 2/3] feature: support multibyte strings in substrReplace

refs: https://github.com/laravel/framework/issues/57838
---
 src/Illuminate/Support/Str.php   | 14 +++++++++++---
 tests/Support/SupportStrTest.php |  2 ++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/Illuminate/Support/Str.php b/src/Illuminate/Support/Str.php
index cccff1a75f6a..b5c3bad8a187 100644
--- a/src/Illuminate/Support/Str.php
+++ b/src/Illuminate/Support/Str.php
@@ -1747,11 +1747,19 @@ public static function substrCount($haystack, $needle, $offset = 0, $length = nu
      */
     public static function substrReplace($string, $replace, $offset = 0, $length = null)
     {
-        if ($length === null) {
-            $length = mb_strlen($string);
+        $encoding = 'UTF-8';
+        $strlen = mb_strlen($string, $encoding);
+
+        if ($offset < 0) {
+            $offset = $offset < -$strlen ? 0 : $strlen + $offset;
         }
 
-        return substr_replace($string, $replace, $offset, $length);
+        $length = is_null($length) ? $strlen - $offset : max($length, 0);
+
+        $start = mb_substr($string, 0, $offset, $encoding);
+        $end = mb_substr($string, $offset + $length, $strlen - ($offset + $length), $encoding);
+
+        return $start . $replace . $end;
     }
 
     /**
diff --git a/tests/Support/SupportStrTest.php b/tests/Support/SupportStrTest.php
index 425966353d29..6a646c70c475 100755
--- a/tests/Support/SupportStrTest.php
+++ b/tests/Support/SupportStrTest.php
@@ -1262,6 +1262,8 @@ public function testSubstrReplace()
         $this->assertSame('12:00', Str::substrReplace('1200', ':', 2, 0));
         $this->assertSame('The Laravel Framework', Str::substrReplace('The Framework', 'Laravel ', 4, 0));
         $this->assertSame('Laravel – The PHP Framework for Web Artisans', Str::substrReplace('Laravel Framework', '– The PHP Framework for Web Artisans', 8));
+        $this->assertSame('Laravel – PHP 框架的网络专家', Str::substrReplace('Laravel 的网络专家', '– PHP 框架', 8, 0));
+        $this->assertSame('Laravel – PHP Фреймворк для веб-мастеров', Str::substrReplace('Laravel для веб-мастеров', ' – PHP Фреймворк', 7, 0));
     }
 
     public function testTake()

From ac493d16131cdf0793ebb410c221bf6fbcc1038c Mon Sep 17 00:00:00 2001
From: Artyom Osepyan <art@osepyan.ru>
Date: Fri, 21 Nov 2025 01:14:25 +0300
Subject: [PATCH 3/3] style: fix code style

---
 src/Illuminate/Support/Str.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Illuminate/Support/Str.php b/src/Illuminate/Support/Str.php
index b5c3bad8a187..235dbc0cc520 100644
--- a/src/Illuminate/Support/Str.php
+++ b/src/Illuminate/Support/Str.php
@@ -1759,7 +1759,7 @@ public static function substrReplace($string, $replace, $offset = 0, $length = n
         $start = mb_substr($string, 0, $offset, $encoding);
         $end = mb_substr($string, $offset + $length, $strlen - ($offset + $length), $encoding);
 
-        return $start . $replace . $end;
+        return $start.$replace.$end;
     }
 
     /**