Different PHPSESSID between Node.js & PHP

I'm building a chat app in Node.js which is only accessible when a user is logged in via my Wordpress blog. My blog runs on port 80, the chat app on 3000.

I have followed this guide on sharing a session between node and PHP. I can get the data stored into Redis, but the PHPSESSID in Node does not match the Wordpress one, why?

EDIT

PHP - functions.php

function init_session() {
  require('redisSessionHandler.php');
  session_start();
  echo session_id();
}
add_action('init', 'init_session', 1);

This prints out the following session ID: pmlmvsst770hj2qsjjm9gt6ja4

Node - index.js

var app = require("http").createServer(handler),
    fs = require("fs"),
    redis = require("redis"),
    co = require("./cookie.js");

app.listen(7070);

function handler(req, res){
    fs.readFile(__dirname + "/index.html", function(err, data){
        if(err){
            res.writeHead(500);
            return res.end("Error loading index.html");
        } else {
            res.writeHead(200);
            res.end(data);
        }
    });

    var cookieManager = new co.cookie(req.headers.cookie),
        clientSession = new redis.createClient();

    console.log(cookieManager.get("PHPSESSID"));

    clientSession.get("sessions/"+cookieManager.get("PHPSESSID"), function(error, result){
      console.log(result);
    });
}

This prints out the following session ID: cv4dsufrkjk29njbfcht0rq015

Here's a link to cookie.js: https://gist.github.com/nickreffitt/5005071