Fatal error: Uncaught Error: Class 'DataItem' not found in /opt/lampp/htdocs/dhtmlxSuite_v5.1/samples/dhtmlxTreeView/common/connector/update.php:12 Stack trace: #0 {main} thrown in /opt/lampp/htdocs/dhtmlxSuite_v5.1/samples/dhtmlxTreeView/common/connector/update.php on line 12