Which version to use for PHP and 'AJAX'?

function makeEditor() {
var oFCKeditor = new FCKeditor( 'MyTextarea' ) ;
oFCKeditor.BasePath = "/fckeditor/" ;
oFCKeditor.ReplaceTextarea() ;
}

function submitComment() {
   var ed = FCKeditorAPI.GetInstance('MyTextarea') ;
   httpRequest = getHTTPObject(); //deffined elsewhere
   var postdata = '&content='+ed.GetXHTML.str.replace(/&/g, '%26')+'x=y';
   httpRequest.open('POST', url, true);
   httpRequest.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
   httpRequest.setRequestHeader('Content-length', postdata.length);
   httpRequest.onreadystatechange = function() { submitResponse(httpRequest); }; //Where submitResponse is a funtion that would inform the user their comment was recieved by the server.
   httpRequest.send(postdata);
}