Bugfix: call with reference only by direct call

Author: jtkDvlp

src/Cache.php

@@ -55,7 +55,7 @@ public function with($func, $identifier) {
 
     $cachedValue = $this->get($identifier, null);
     $alreadyCached = null !== $cachedValue;
-    $funcResult = call_user_func($func, $cachedValue);
+    $funcResult = $func($cachedValue);
 
     if(false === $alreadyCached) {
       $this->set($identifier, $cachedValue);