Loading XML-file from a php file include

I’ve installed the plugin ‘Allow PHP in Posts and Pages’ to run this script inside a wordpress-page, this trick works in my Joomla-site but I can’t seem to get it working.

The page I’m trying to create is at my test-website.

I’ve copied some of the code below, but I think it stops executing after the xhttp.open(“GET” …

// create XML request
	if (window.XMLHttpRequest) {
		xhttp = new XMLHttpRequest();
	} else {
		// support for IE 5/6
		xhttp = new ActiveXObject("Microsoft.XMLHTTP");
	} 

	// load XML file
	xhttp.open("GET", "https://www.maartenprovo.be/projects/form/pricing.xml", false);
	xhttp.send(null);
	xmlDoc = xhttp.responseXML;

What’s wrong and how can I solve it?