Dojo xhr get not setting XmlHttpRequest
===

I'm using Dojo 1.7.2 and I try the following code

    var request = xhr.get({
    		url: location,
    		content : content,
    		load : function( data ){
    			for( var x in data )
    				{
    					alert ( x + data[x] );
    				}
    		},
    		error : function()
    		{
    			alert( 'Had an eror' );
    		},
    		handleAs : 'json'
    	});
    	

Then in php i do the following to try and detect the xmlhttprequest 


    function isAjax(){
    	
    	$ajax = (isset( $_SERVER[ 'HTTP_X_REQUESTED_WITH' ] ) ) &&
    		( strtolower( $_SERVER[ 'HTTP_X_REQUESTED_WITH' ] ) ==  'xmlhttprequest' );
    	
    	return $ajax;
    }

But the isAjax function returns false.

If I do <code>xhr.post</code> then it works fine. I'm thinking this is just a side effect of using GET instead of POST? Is that it or is it something else that I'm not checking for.