Reverse Ajax implementation using php

Question

I am looking to implement reverse ajax in my application which is using PHP and jquery. I have googled a bit about it and found XAJA but that seems to be a paid application. Is there an open source application available for the same or has someone implemented it?

Some pointers or hints would be very helpful.

Thanks in advance.

Answer 1

I know of two types of reverse AJAX:
1- Polling
2- Pushing

I think polling is rather easier to implement, you just have your javascript make a regular request to the server every time interval, and when the server have some data for it it will respond. Its like a ping and some call it heartbeat, but its the very obvious solution for this problem. However it may easily overload the server.

EDIT Simple polling Example code:
Server-Side:

<?php
//pong.php php isn't my main thing but tried my best!
$obj = new WhatsNew();
$out = "";
if ($obj->getGotNew()){
    $types = new array();
    foreach ($obj->newStuff() as $type)
        {
            $new = array('type' => $type);
            $types[] = $new;
        }

    $out = json_encode($types);
}
else{
    $out = json_encode(array('nothingNew' => true));
}

Client-Side:

function ping(){
    $.ajax(
        {

            url : "pong.php",
            success : function (data){
                data = JSON.parse(data),
                if (data['nothingNew'])
                    return;
                for(var i in data){
                    var type = data[i]['type'];
                    if (type && incomingDataHandlers[type]){
                        incomingDataHandlers[type]();
                    }
                }


        });
}
incomingDataHandlers = {
    comments: function () {
        $.ajax({
            url: "getComments.php",
            method: "GET",
            data: getNewCommentRequsetData() // pass data to the server;
            success : function (data){
                //do something with your new comments
            }
        });
    },
    message: function (){
        $.ajax({
            url: "getMessages.php",
            method: "GET",
            data: getNewMessageRequestData() // pass data to the server;
            success : function (data){
                //do something with your new messages
            }
        });
    }
}
$(docment).ready(function () {
    setInterval(ping, 1000);
})

Answer 2

You are looking for what they call "long poll" - I did a "long poll php" and I got this thread on stack overflow:

How do I implement basic "Long Polling"?