diff --git a/index.php b/index.php
index 15f7039..2b679ec 100644
--- a/index.php
+++ b/index.php
@@ -44,8 +44,8 @@ if (isset($_SESSION['files'])
 $filter='';
 if (isset($_GET['f'])) {
   if ($_GET['f'] != '') {
-    $t = array('(' => '\(', ')' => '\)');
-    $f = strtr($_GET['f'], $t);
+    $tr = array('(' => '\(', ')' => '\)');
+    $f = strtr($_GET['f'], $tr);
     $files = array_values(preg_grep('/.*'.$f.'.*/i', $files));
     $filter='&f='.$_GET['f'];
   }