Custom PHP SessionHandler class Write issue - php

Question

I'm creating my own custom SessionHandler to store my session information in a postgresql 9.3 database and I'm having a problem where the session data passed to the write() method isn't being written to the database, but the session name is??
Things that I know for a fact
My custom class is handling the sessions when session_start() is called - as tested with echoing output from the various methods and no session files are being created in /tmp
The $session_data arg in write() contains the proper serialized string as shown by echoing the contents in the write() method.
$session_name is being written to the database just fine and so is a BLANK serialized string a:0:{}.
Things I'm confused about:
Echoing the contents of $_SESSION['test_var1'] shows the correct value stored, even if read() is empty or returning no value??
If the session name is saved in the DB just fine, why isn't the session data?
Server Configuration
OS: Gentoo
Database: Postgresql 9.3
Web Server: NGINX 1.7.6
PHP 5.5.18 connected to NGINX via FPM
PHP ini session settings
session.save_handler = user
session.use_strict_mode = 1
session.use_cookies = 1
session.cookie_secure = 1
session.use_only_cookies = 1
session.name = _g
session.auto_start = 0
session.serialize_handler = php_serialize
class SessionManagement implements SessionHandlerInterface {
private $_id = '';
private $_link = null;
public function __construct() {
session_set_save_handler(
[$this, 'open'],
[$this, 'close'],
[$this, 'read'],
[$this, 'write'],
[$this, 'destroy'],
[$this, 'gc']
);
}
public function open($save_path, $session_id) {
echo 'open called<br/>';
$this->_id = $session_id;
$this->_link = new PDO('pgsql:host=' . $_SERVER['DB_HOST'] . ';dbname=' . $_SERVER['DB_DB'],
$_SERVER['DB_USER'],
$_SERVER['DB_PASS']);
}
public function close() {
echo 'close called<br/>';
}
public function destroy($session_id) {
echo 'destroying '.$session_id, '<br/>';
}
public function gc($maxlifetime) {
echo 'GC called<br/>';
}
public function read($session_name) {
$name = $this->_id.'_'.$session_name;
$sql = 'SELECT session_data FROM sessions WHERE session_name = :name';
if ($rel = $this->_link->prepare($sql)) {
if ($rel->execute([':name' => $name])) {
return $rel->fetch(PDO::FETCH_ASSOC)['session_data'];
} else {
return false;
}
} else {
return false;
}
return '';
}
public function write($session_name, $session_data) {
echo 'Session data: '.$session_data.'<br/>';
$name = $this->_id . '_' . $session_name;
$data = $session_data;
$sql = "SELECT 1 FROM sessions WHERE session_name = :name";
if ($rel = $this->_link->prepare($sql)) {
if ($rel->execute([':name' => $name])) {
if ($rel->rowCount()) {
echo 'Updating...<br/>';
$sql = 'UPDATE sessions SET session_data = :data WHERE session_name = :name';
if ($rel = $this->_link->prepare($sql)) {
if ($rel->execute([':name' => $name, ':data' => $data])) {
echo 'Update success...<br/>';
} else {
echo 'Update failed...<br/>';
var_dump($rel->errorInfo());
}
}
} else {
echo 'Inserting...<br/>';
$sql = 'INSERT INTO sessions (session_name, session_data) ';
$sql .= 'VALUES(:name, :data)';
if ($rel = $this->_link->prepare($sql)) {
if ($rel->execute([':name' => $name, ':data' => $data])) {
echo 'Insert success...<br/>';
} else {
echo 'Insert failed...<br/>';
var_dump($rel->errorInfo());
}
}
}
}
}
}
}
Test code:
new SessionManagement();
session_start();
$_SESSION['test_var1'] = 'some test data';
session_write_close(); // Making sure writing is finished
echo $_SESSION['test_var1'];
Output via test page
open called
Session data: a:1:{s:9:"test_var1";s:14:"some test data";}
Inserting...
Insert success...
close called
some test data
Relevant database fields
session_name: _g_h8m64bsb7a72dpj56vgojn6f4k3ncdf97leihcqfupg2qtvpbo20
session_data: a:0:{}
I'm not sure if this is a database issue or a PHP issue. I've been messing with this for a few days now and decided it was time to ask the community. Hopefully someone has some insight as to what the problem is.

Answer 1

I think you must initialize PDO object outside of the Open function handler and the class itself
try to access to your PDO Object with a Global value or through a static variable.
This is my implementation with MYSQL for my project :
class Core_DB_SessionHandler implements SessionHandlerInterface
{
protected $options = array(); // Options de la session
protected static $db = NULL; // Acceder a la BDD
public function __construct($options, $pdo) {
$this->options = $options;
self::$db = $pdo;
}
public function open($savePath, $sessionName) {
$now = time();
$req = self::$db->prepare("DELETE FROM tbl_sessions WHERE expire < '{1}' ");
$req->execute(array($now));
return TRUE;
}
public function close() {
$this->gc(ini_get('session.gc_maxlifetime'));
}
public function read($id) {
$now = time();
$stmt = self::$db->query("SELECT data FROM tbl_sessions WHERE sid = '$id AND expire < '$now'");
$result = $stmt->fetchColumn();
return $result;
}
public function write($id, $data) {
if (array_key_exists('TIMEOUT', $_SESSION)) {
$newExp = $_SESSION['TIMEOUT'];
}
else {
$newExp = time() + $this->options['time_limiter'];
}
try {
$req = self::$db->prepare('INSERT INTO tbl_sessions (sid, data, expire) VALUES (:sid, :data, :expire)
ON DUPLICATE KEY UPDATE data = :data, expire = :expire');
$vals = array('sid' => $id, 'data' => $data, 'expire' => $newExp);
$req->execute($vals);
return TRUE;
}
catch (PDOException $e) {
throw new Core_Exception(sprintf('PDOException was thrown when trying to write the session data: %s', $e->getMessage()), 0, $e);
}
}
public function destroy($id) {
$stmt = self::$db->prepare("DELETE FROM tbl_sessions WHERE sid = '{1}'");
$stmt->execute(array($id));
//return ($stmt->rowCount() === 1) ? true : false;
return TRUE;
}
public function gc($maxlifetime) {
$now = time();
$req = self::$db->prepare("DELETE FROM tbl_sessions WHERE expire < '{1}' ");
$req->execute(array($now));
return TRUE;
}
}
and i initialize handler like this :
$handler = new Core_DB_SessionHandler($MyOptions, $MyPDO);
if (PHP5) {
if (!session_set_save_handler($handler, TRUE)) {
throw new Core_Exception('Erreur lors de l\'init des sessions !');
}
}
nb : In your Table structure don't use autoincrement for ID

Answer 2

Well, I've solved my problem, but it's hard to say if this fix was actually the problem in the first place.
In the read method, I changed the follow:
return $rel->fetch(PDO::FETCH_ASSOC)['session_data'];
to
$data $rel->fetch(PDO::FETCH_ASSOC)['session_data'];
return $data;
After this the session was writing $session_data to the database without any problem. That's all well and dandy, but it doesn't explain why it didn't work in the first place. I mainly say this because upon switching the statement back everything continued to work. As in, I can't reproduce the issue now. So it's hard for me to even say that this was the problem in the first place.
Hopefully this helps someone. I've been unable to find more information about it, but it something does show up I'll be sure to add it here.