[8.x] increase performance of Str::before by over 60%. (#34642)

* [8.x] increase performance of Str::before by over 50%.

* [8.x] refactor code for readability and a further 10% speed gain.

src/Illuminate/Support/Str.php

@@ -107,7 +107,13 @@ public static function ascii($value, $language = 'en')
      */
     public static function before($subject, $search)
     {
-        return $search === '' ? $subject : explode($search, $subject)[0];
+        if ($search === '') {
+            return $subject;
+        }
+
+        $result = strstr($subject, (string) $search, true);
+
+        return $result === false ? $subject : $result;
     }
 
     /**