solution for 'PHP Fatal error: Cannot pass parameter 2 by reference' in SPARQL Endpoint

loki/sparql/index.php

@@ -12,7 +12,7 @@ if(isset($_GET['query']) AND !empty($_GET['query']) AND
    isset($_GET['format']) AND !empty($_GET['format']) AND in_array(strtolower($_GET['format']), $formats)) {
     $sparql = new LokiUtlSparql();
 
-    echo $sparql->process_sparql($_GET['query'],null,strtolower($_GET['format']));
+    echo $sparql->process_sparql($_GET['query'],$a=null,strtolower($_GET['format']));
 } else {
     require_once './form.php';
 }