Question

I’m trying to create a very simple message board (author, text, and date written) that will auto-update every few moments to see if a new message has arrived, and if it has, auto load the latest message(s).

I’m proficient in PHP, but my knowledge in AJAX is lacking.

The way I see it, I would have to create a PHP file called get_messages.php that would connect to a database and get through a $_GET variable return all posts beyond date X, and then I would somehow through jquery call this PHP file every few minutes with $_GET=current time?
Does this sound correct?

How would I got about requesting and returning the data to the web page asynchronously?

Answer 1

You’re pretty close, you’ll need a PHP script that can query the database for your results. Next, you’ll want to transfigure those results into an array, and json_encode() them:

$results = getMyResults();
/* Assume this produce the following Array:
   Array(
     "id" => "128","authorid" => "12","posttime" => "12:53pm",
     "comment" => "I completely agree! Stackoverflow FTW!"
   );
*/
print json_encode($results);
/* We'll end up with the following JSON:
   {
     {"id":"128"},{"authorid":"12"},{"posttime":"12:53pm"},
     {"comment":"I completely agree! Stackoverflow FTW!"}
   }
*/

Once these results are in JSON format, you can better handle them with javascript. Using jQuery’s ajax functionality, we can do the following:

setInterval("update()", 10000); /* Call server every 10 seconds */

function update() {
  $.get("serverScript.php", {}, function (response) {
    /* 'response' is our JSON */
    alert(response.comment);
  }, "json");
}

Now that you’ve got your data within javascript (‘response’), you are free to use the information from the server.