Merge pull request #156 from Runalyze/final

add file_exists check for file driver delete function

Author: khoaofgod

phpfastcache/3.0.0/drivers/files.php

@@ -118,7 +118,7 @@ function driver_get($keyword, $option = array()) {
 
     function driver_delete($keyword, $option = array()) {
         $file_path = $this->getFilePath($keyword,true);
-        if(@unlink($file_path)) {
+        if(file_exists($file_path) && @unlink($file_path)) {
             return true;
         } else {
             return false;