Using node.js to store PHP sessions


We use sessions when we want to preserve certain data across subsequent accesses. PHP allows us to use different handlers when we’re using sessions. The default one is filesystem, but we can change it with session.save_handler in the php.ini. session.save_handler defines the name of the handler which is used for storing and retrieving data associated with a session. We also can create our own handler to manage sessions. In this post we’re going to create a custom handler to store sessions in a node.js service. Let’s start:

Imagine we’ve got the following php script:

session_start();

if (!isset($_SESSION["gonzalo"])) $_SESSION["gonzalo"] = 0;
$_SESSION["gonzalo"]++;
$_SESSION["arr"] = array('key' => uniqid());
var_dump($_SESSION);

A simple usage of sessions with PHP. If we reload the page our counter will be incremented by one. We’re using the default session handler. It works without any problem.

The idea is create a custom handler to use a server with node.js to store the session information instead of filesystem. To create custom handlers we need to use the PHP function: session_set_save_handler and rewrite the callbacks for: open, close, read, write, destroy and gc. PHP’s documentation is great. My proposal is the following one:

Our custom handler:

class NodeSession
{
    const NODE_DEF_HOST = '127.0.0.1';
    const NODE_DEF_PORT = 5672;

    static function start($host = self::NODE_DEF_HOST, $port = self::NODE_DEF_PORT)
    {
        $obj = new self($host, $port);
        session_set_save_handler(
            array($obj, "open"),
            array($obj, "close"),
            array($obj, "read"),
            array($obj, "write"),
            array($obj, "destroy"),
            array($obj, "gc"));
        session_start();
        return $obj;
    }

    private function unserializeSession($data)
    {
        if(  strlen( $data) == 0) {
            return array();
        }

        // match all the session keys and offsets
        preg_match_all('/(^|;|\})([a-zA-Z0-9_]+)\|/i', $data, $matchesarray, PREG_OFFSET_CAPTURE);
        $returnArray = array();

        $lastOffset = null;
        $currentKey = '';
        foreach ( $matchesarray[2] as $value ) {
            $offset = $value[1];
            if(!is_null( $lastOffset)) {
                $valueText = substr($data, $lastOffset, $offset - $lastOffset );
                $returnArray[$currentKey] = unserialize($valueText);
            }
            $currentKey = $value[0];

            $lastOffset = $offset + strlen( $currentKey )+1;
        }

        $valueText = substr($data, $lastOffset );
        $returnArray[$currentKey] = unserialize($valueText);

        return $returnArray;
    }
    
    function __construct($host = self::NODE_DEF_HOST, $port = self::NODE_DEF_PORT)
    {
        $this->_host = $host;
        $this->_port = $port;
    }

    function open($save_path, $session_name)
    {
        return true;
    }

    function close()
    {
        return true;
    }

    public function read($id)
    {
        return (string) $this->send(__FUNCTION__, array('id' => $id));
    }

    public function write($id, $data)
    {
        try {
            $this->send(__FUNCTION__, array(
                'id'       => $id,
                'data'     => $data,
                'time'     => time(),
                'dataJSON' => json_encode($this->unserializeSession($data))));
            return true;
        } catch (Exception $e) {
            return false;
        }
    }

    public function destroy($id)
    {
        try {
            $this->send(__FUNCTION__, array('id' => $id));
        } catch (Exception $e) {
            return false;
        }
         return true;
    }

    function gc($maxlifetime)
    {
        try {
            $this->send(__FUNCTION__, array('maxlifetime' => $maxlifetime, 'time' => time()));
        } catch (Exception $e) {
            return false;
        }
        return true;
    }

    private function send($action, $params)
    {
        $params = array('action' => $action) + $params;
        return file_get_contents("http://{$this->_host}:{$this->_port}?" . http_build_query($params));
    }
}

Our node.js server:

var http = require('http'),
    url  = require('url'),
    session = require('nodePhpSessions').SessionHandler;

var sessionHandler = new session();

var server = http.createServer(function (req, res) {
    var parsedUrl = url.parse(req.url, true).query;
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end(sessionHandler.run(parsedUrl));
});

server.listen(5672, "127.0.0.1", function() {
  var address = server.address();
  console.log("opened server on %j", address);
});

As we can see we need the node.js module nodePhpSessions. You can easily install with:

npm install nodePhpSessions

You can see nodePhpSessions library here.

The library is tested with nodeunit. Without TDD is very hard to test things such as garbage collector.:

var session = require('nodePhpSessions').SessionHandler;
var sessionHandler = new session();
var parsedUrl;

exports["testReadUndefinedSession"] = function(test){
    parsedUrl = { action: 'read', id: 'ts49vmf0p732iafr25mdu8gvg2' };
    test.equal(sessionHandler.run(parsedUrl), undefined);
    test.done();
};

exports["oneSessionShouldReturns1"] = function(test){
    parsedUrl = {
        action: 'write',
        id: 'ts49vmf0p732iafr25mdu8gvg2',
        data: 'gonzalo|i:1;arr|a:1:{s:3:"key";s:13:"4e2b1a40d136a";}',
        time: '1311447616',
        dataJSON: '{"gonzalo":1,"arr":{"key":"4e2b1a40d136a"}}' };
    sessionHandler.run(parsedUrl);

    parsedUrl = { action: 'readAsArray', id: 'ts49vmf0p732iafr25mdu8gvg2' };
    test.equal(sessionHandler.run(parsedUrl).gonzalo, 1);
    test.done();
};

exports["oneSessionShouldReturns2"] = function(test){
    parsedUrl = {
        action: 'write',
        id: 'ts49vmf0p732iafr25mdu8gvg2',
        data: 'gonzalo|i:2;arr|a:1:{s:3:"key";s:13:"4e2b1a40d136a";}',
        time: '1311447616',
        dataJSON: '{"gonzalo":2,"arr":{"key":"4e2b1a40d136a"}}' };
    sessionHandler.run(parsedUrl);
    parsedUrl = { action: 'readAsArray', id: 'ts49vmf0p732iafr25mdu8gvg2' };
    test.equal(sessionHandler.run(parsedUrl).gonzalo, 2);
    test.done();
};

exports["destroySession"] = function(test){
    parsedUrl = {
        action: 'destroy',
        id: 'ts49vmf0p732iafr25mdu8gvg2'};
    sessionHandler.run(parsedUrl);

    parsedUrl = { action: 'readAsArray', id: 'ts49vmf0p732iafr25mdu8gvg2' };
    test.equal(sessionHandler.run(parsedUrl), undefined);

	test.done();
};

exports["garbageColector"] = function(test){
    parsedUrl = {
        action: 'write',
        id: 'session1',
        data: 'gonzalo|i:1;arr|a:1:{s:3:"key";s:13:"4e2b1a40d136a";}',
        time: '1111111200',
        dataJSON: '{"gonzalo":1,"arr":{"key":"4e2b1a40d136a"}}' };
    sessionHandler.run(parsedUrl);

    parsedUrl = {
        action: 'write',
        id: 'session2',
        data: 'gonzalo|i:1;arr|a:1:{s:3:"key";s:13:"4e2b1a40d136a";}',
        time: '1111111100',
        dataJSON: '{"gonzalo":1,"arr":{"key":"4e2b1a40d136a"}}' };
    sessionHandler.run(parsedUrl);

    parsedUrl = { action: 'gc', maxlifetime: '100', time: '1111111210'};
    sessionHandler.run(parsedUrl);

    parsedUrl = { action: 'readAsArray', id: 'session2' };
    test.equal(sessionHandler.run(parsedUrl), undefined);

    parsedUrl = { action: 'readAsArray', id: 'session1' };
    test.equal(sessionHandler.run(parsedUrl).gonzalo, 1);

    test.done();
};

Here you can see the output of the tests:

nodeunit testNodeSessions.js 

testNodeSessions.js
✔ testReadUndefinedSession
✔ oneSessionShouldReturns1
✔ oneSessionShouldReturns2
✔ destroySession
✔ garbageColector

OK: 6 assertions (5ms)

Now we change the original PHP script to:

include_once 'NodeSessions.php';
NodeSession::start();

if (!isset($_SESSION["gonzalo"])) $_SESSION["gonzalo"] = 0;
$_SESSION["gonzalo"]++;
$_SESSION["arr"] = array('key' => uniqid());
var_dump($_SESSION);

We start the node.js server:

node serverSessions.js 

Now if we reload our script in the browser we will see the same behaviour, but now our sessions are stored in the node.js server.

array(2) {
  ["gonzalo"]=>
  int(16)
  ["arr"]=>
  array(1) {
    ["key"]=>
    string(13) "4e2a9f6a966f4"
  }
}

This kind of techniques are good when clustering PHP applications.

Full code is available on github (node server, PHP handler, tests and examples) here.

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About Gonzalo Ayuso

Web Architect specialized in Open Source technologies. PHP, Python, JQuery, Dojo, PostgreSQL, CouchDB and node.js but always learning.

Posted on July 25, 2011, in node.js, npm, php, Technology and tagged , , , , . Bookmark the permalink. 12 Comments.

  1. I don’t get it. Why wouldn’t you just use memcached to distribute the sessions? This seems like a lot of work to solve a problem that didn’t exist. What’d I miss?

    • Gonzalo Ayuso

      Memcached is a good solution to store php sessions. Another way is to use a noSql database such as redis or couchdb (I’ve got a site with sessions on couchDb and works fine) to ensure persistence (I don’t like to persist data in mysql with memcached).

      That’s an experiment. Why I’ve done it? The idea is the following one. I like to use comet solution with node.js and socket.io (see my previous post). I’ve got a problem with it. If my whole app is built on PHP and it’s behind a session based auth system I need to share the autn between PHP server and node.js socket.io instance (non auth user are not able to acess to socket.io websockets).

      With this solution I can share session easily. OK I can store session on memcached and check session with PHP and node.js, but this idea was in mind I wanted to develop a working prototype. If I want to monitor the session, or even modify or share them, it’s trivial. Anyway, as I said before If you don’t want exotic solutions to solve the problem of distributed sessions, use memcached. Anyway I’ve read big sites are leaving memcached solutions. They’re moving to noSQL solutions. My prototype is not a real noSQL database (it hasn’t any map-reduce), but it’s a simple key-value database (without persistance)

  2. Do you have some perf stats with the node solution?

    • You hit me. I didn’t check the performance. In fact it’s only an experiment. Probably the performance is good. All is stored in memory. There isn’t persistent storage. But I’m not sure how this solution will scale.

  3. This works very well, but took me a moment to work out what would not have seemed obvious to some… I think you need to point out that the parsedUrl variable is an object that contains the session ID and that in order to write to a session variable or read from the session handler you must pass the session id into each of these functions. It would speed up the thought process for noobs

    • Probably I didn’t understand properly, but session id must be set each time. Tests try to simulate the real behaviour of PHP sessions

  4. Kindly can you pls guide with the query below

    How do I pass php session to socket.io ?
    How to detect socket expiration in socket.io ?

    https://groups.google.com/forum/?fromgroups#!searchin/nodejs/authentication/nodejs/D0jTf0Kleyc/discussion

    Thank You

    • Gonzalo Ayuso

      That’s the problem: we have different environments: php (session based auth) and node.js. We need to share the auth token. I haven’t seen any good (and not very exotic) solution yet. Maybe a Oauth2, but not sure.

  5. Hi, thanks for this solution. I can’t find the way to destroy the session for real, do I have to use NodeSession::destroy(session_id()); or session_destroy() from php should work as expected?

    • In this example both are the same. Since you’re using the stream wrapper (when you execute NodeSession::start();) you’re telling to your PHP script to execute NodeSession::destroy (with the proper session id) when you call to session_destroy().

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