Use mbstring proxy methods (#12104)

* Use mbstring proxy methods

* Avoid using strtolower/strtoupper if mbstring is not available to prevent possible unicode problems

1 files changed, 21 insertions, 1 deletions

diff --git a/core/Common.php b/core/Common.php
index f884d9fe2f..7430cc6662 100644
--- a/core/Common.php
+++ b/core/Common.php
@@ -232,7 +232,27 @@ class Common
             return mb_strtolower($string, 'UTF-8');
         }
 
-        return strtolower($string);
+        // return unchanged string as using `strtolower` might cause unicode problems
+        return $string;
+    }
+
+    /**
+     * Multi-byte strtoupper() - works with UTF-8.
+     *
+     * Calls `mb_strtoupper` if available and falls back to `strtoupper` if not.
+     *
+     * @param string $string
+     * @return string
+     * @api
+     */
+    public static function mb_strtoupper($string)
+    {
+        if (function_exists('mb_strtoupper')) {
+            return mb_strtoupper($string, 'UTF-8');
+        }
+
+        // return unchanged string as using `strtoupper` might cause unicode problems
+        return $string;
     }
 
     /*