I am new to these tecnologies.

I want to get realtime visitor for each products for my site. I mean a notify like "X users seeing this product".

Whenever an user connects to a product counter will be increased for this product and when disconnects counter will be decreased just for this product.

I tried to search a lots of documents but i got confused.

I am using Predis Library for PHP.

What i have done may totaly be wrong. I am not sure Where to put createClient , When to subscribe & When to unsubscribe.

What I have done yet:

On product detail page:

$key = "product_views_".$product_id;
$counter = $redis->incr($key);


$redis->publish("productCounter", json_encode(array("product_id"=> "1000", "counter"=> $counter )));

In app.js

var app = require('express')()
, server = require('http').createServer(app)
, socket = require('socket.io').listen(server,{ log: false })
, url = require('url')
, http= require('http')
, qs = require('querystring')
,redis   = require("redis");

var connected_socket = 0;

server.listen(8080);

var productCounter  = redis.createClient();     
productCounter.subscribe("productCounter");

productCounter.on("message", function(channel, message){
    console.log("%s, the message : %s", channel, message);
    io.sockets.emit(channel,message);
}

productCounter.on("unsubscribe", function(){
    //I think to decrease counter here, Shold I? and How?
}

io.sockets.on('connection', function (socket) {
    connected_socket++;
    socket_id = socket.id;
    console.log("["+socket_id+"] connected");

    socket.on('disconnect', function (socket) {
           connected_socket--;
           console.log("Client disconnected");
           productCounter.unsubscribe("productCounter");
    });

})

Thanks a lot for your answers!