code: function(url, params, onload, onerror)
  	{
  		return new mxXmlRequest(url, params).send(onload, onerror);
  	}
docs: Function: post
  
  Posts the specified params to the given URL *asynchronously* and invokes
  the given functions depending on the request status. Returns the
  <mxXmlRequest> in use. Both functions take the <mxXmlRequest> as the
  only parameter. Make sure to use encodeURIComponent for the parameter
  values.
  
  Example:
  
  (code)
  mxUtils.post(url, 'key=value', function(req)
  {
  mxUtils.alert('Ready: '+req.isReady()+' Status: '+req.getStatus());
  // Process req.getDocumentElement() using DOM API if OK...
  });
  (end)
  
  Parameters:
  
  url - URL to get the data from.
  params - Parameters for the post request.
  onload - Optional function to execute for a successful response.
  onerror - Optional function to execute on error.