How can I pass/access PHPSESSID cookie value from the socket.io websocket?

Question

I need to pass the value of the PHPSESSID cookie when a client try to connect to a socket.io websocket.

I tried to use socket.handshake.headers, but for some reason the PHPSESSID was not passed.

I tried to emit a connect event to send the cookie value. But I still can't seems to be able to do this.

Here is what I have done

This is my websocket server code

var env = require('./config');

var app = require('express')();
var server = require('http').Server(app);

var io = require('socket.io')(server);

var clients = [];

server.listen(env.socket.port, env.socket.host, function () {
  var host = server.address().address;
  var port = server.address().port;

  console.log('Websocket running at http://%s:%s', host, port);
});

app.get('/', function (req, res) {
    res.send('Welcome!');
});

io.on('connection', function (socket) {

    //console.log(socket.handshake.headers);
    clients.push(socket);

    socket.on('connect', function(msg){
        console.log('PHPSESSID: ' + msg);
    });

    socket.on('chat', function(msg){
        console.log('message: ' + msg);
    });

    socket.emit('chat', { hello: 'world' });
});

Here is my client code

<script>

    $(function(){
       var socket = io.connect('https://10.0.4.18:8020');

       socket.emit('connect', { 'sessionId' : '<?php echo $_COOKIE['PHPSESSID']; ?>' });

      $('#f').click(function(e){
            e.preventDefault();

            if($('#m').val() == '')
                return;

            socket.emit('chat', $('#m').val());
            $('#m').val('');
            return false;
      });

      socket.on('chat', function(msg){
        $('#messages').append($('<li>').text(msg));
      });
    });

</script>

I am expecting to print the json string with the sessionId to the server's console.

How can I pass/access the PHPSESSID value from the websocket?