escape qrencode arguments in multibyte-safe way

includes/functions.php

@@ -332,3 +332,17 @@ function cache($key, $callback)
         return $data;
     }
 }
+
+// insspired by
+// http://markushedlund.com/dev/php-escapeshellarg-with-unicodeutf-8-support
+function mb_escapeshellarg($arg)
+{
+    $isWindows = strtolower(substr(PHP_OS, 0, 3)) === 'win';
+    if ($isWindows) {
+        $escaped_arg = str_replace(array('"', '%'), '', $arg);
+    } else {
+        $escaped_arg = str_replace("'", "'\\''", $arg);
+    }
+    return "\"$escaped_arg\"";
+}
+