diff --git a/lib/Doctrine/Common/Cache/PhpFileCache.php b/lib/Doctrine/Common/Cache/PhpFileCache.php
index <HASH>..<HASH> 100644
--- a/lib/Doctrine/Common/Cache/PhpFileCache.php
+++ b/lib/Doctrine/Common/Cache/PhpFileCache.php
@@ -64,6 +64,10 @@ class PhpFileCache extends FileCache
         if ( ! is_file($filename)) {
             return false;
         }
+        
+        if ( ! is_readable($filename)) {
+            return false;
+        }
 
         $value = include $filename;
when the file is found but is not readable by the user, then prevent error `Warning: include(tmp/cache/tracker/piwikcache_general.php): failed to open stream: Permission denied in vendor/doctrine/cache/lib/Doctrine/Common/Cache/PhpFileCache.php on line <I>