asked on

Can't save session data into the database

Hi everybody.
I'm trying to save PHP sessions to the database using mysqli but I'm struggking with an error I don't understand.

I use some classes autoloaded by Composer and everything worked fine until I have added the new classes Session and SessionModel. But first let me introduce the base class for DB connection, DbModel. Here the constructor:

<?php

namespace Emgie\EmgieDB;

use Emgie\EmgieConfig\EmgieConfigurator;

require __DIR__ . '/../../vendor/autoload.php';

if (!class_exists('DB')) {

  class DbModel
  {
    private $config;
    protected static $conn = null;
    protected $tableName;

    public function __construct($tableName)
    {
      $this->tableName = $tableName;
      $ec = new EmgieConfigurator();
      $this->config = $ec->getConfig();
      $this->connect();
    }

    private function connect()
    {
      if (!is_null(self::$conn)) {
        // a connection has already been established
        return;
      }

      self::$conn = new \mysqli($this->config->database->dbHost, $this->config->database->dbUserName, $this->config->database->dbPassword, $this->config->database->dbName);

      if (self::$conn->connect_error) {
        die("Connection failed: " . self::$conn->connect_errno . ' ' . self::$conn->connect_error);
      }
      self::$conn->set_charset('utf8');
    }
  }
}

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All my ***Model classes extend this base class and they didn't give me any issues until now.

In Session class I have this:

<?php

namespace Emgie\EmgieUtils;

require __DIR__ . '/../../vendor/autoload.php';
/*code found at https://github.com/dominicklee/PHP-MySQL-Sessions*/

class Session
{


  private $model;

  public function __construct()
  {
    $this->model = new SessionModel();

    // Set handler to overide SESSION
    session_set_save_handler(
      array($this, "_open"),
      array($this, "_close"),
      array($this, "_read"),
      array($this, "_write"),
      array($this, "_destroy"),
      array($this, "_gc")
    );
    register_shutdown_function('session_write_close');
    // Start the session
    session_start();
  }

  public function _open()
  {
    return $this->model->checkConnection();
  }

  public function _read($id)
  {
    return $this->model->getSessionData($id);
  }
}

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And here the insterested code inSessionModel

<?php

namespace Emgie\EmgieUtils;

use Emgie\EmgieDB\DbModel;

require __DIR__ . '/../../vendor/autoload.php';

class SessionModel extends DbModel
{

  protected $db;

  public function __construct()
  {
    parent::__construct('sessions');
    $this->db = parent::$conn;
  }

  public function checkConnection()
  {
    if (isset($this->db)) {
      return true;
    }
    return false;
  }

  public function getSessionData($id)
  {
    $query = "SELECT data FROM sessions WHERE id = ?";
    $stmt =  $this->db->stmt_init(); //line 31
    if ($stmt->prepare($query)) {
      $stmt->bind_param("s", $id);
      $stmt->execute();
      $result = $stmt->get_result();
      $row = $result->fetch_assoc();
      $stmt->close();
      return isset($row['data']) ? $row['data'] : '';
    }
    return '';
  }
}

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The open function gives an error; Uncaught Error: Failed to open session: user

Forcing a true result of checkConnection method I get this

Uncaught Error: Call to a member function stmt_init() on null in /***/admin/emgie/emgieUtils/SessionModel.php:31

It looks like $this->db is not set but with the same code it is in every other ***Model class I'm using.
ANy idea.
Thank you for any help

David Favor

This means either $this->db or $this == NULL.

Best to wrap your access of these objects + output an error about which one is NULL.

Based on which is NULL, you'll debug from there.

Marco Gasi

ASKER

Hello David, thank you fro your help. Great suggestion! Now I know something more and I'm going to share it with you:

the model in Session class is correctly initiated (not null)
$this->db is an object in Model constructor...
but $this->db is null in Model checkConnection()!

I'm investigating using this new info (but I still find it really strange)

Marco Gasi

ASKER

I modified the Session class code in order to run the queries from within the class itself instead of use another class and this way above errors don't show up. But I get other errors!

First the new Session code:

<?php

namespace Emgie\EmgieUtils;

require __DIR__ . '/../../vendor/autoload.php';
require_once __DIR__ . '/../../ChromePhp.php';

use Emgie\EmgieDB\DbModel;

class Session
{


  private $model;
  private $db;

  public function __construct()
  {
    $database = new DbModel('sessions');
    
    /*I have added a getter to DbModel in order to access the static property $conn*/  
    $this->db = $database->getConnection();

    // Set handler to overide SESSION
    session_set_save_handler(
      array($this, "_open"),
      array($this, "_close"),
      array($this, "_read"),
      array($this, "_write"),
      array($this, "_destroy"),
      array($this, "_gc")
    );
    register_shutdown_function('session_write_close');
    // Start the session
    session_start();
  }

  public function _open()
  {
    if(is_null($this->db)){
      \ChromePhp::log('db in _open is null');
      return false;
    }
    \ChromePhp::log('db in _open is ok');
    return true;
  }

  public function _close()
  {
    $this->db = null;
  }

  public function _read($id)
  {
    $query = "SELECT data FROM sessions WHERE id = ?";

    $stmt =  $this->db->stmt_init();
    if ($stmt->prepare($query)) {
      $stmt->bind_param("s", $id);
      $stmt->execute();
      $result = $stmt->get_result();
      $row = $result->fetch_assoc();
      $stmt->close();
      \ChromePhp::log('$row[data]');
      \ChromePhp::log($row['data']);
      return $row['data'];
    }
    \ChromePhp::log('_read returns an empty string');
    return '';
    // return $this->model->getSessionData($id);
  }

  public function _write($id, $data)
  {
    $access = time();
    $query = "REPLACE INTO sessions (id, access, data) VALUES (:id, :access, :data)";
    if ($stmt = $this->db->prepare($query)) {
      $stmt->bind_param("sis", $id, $access, $data);
      return $stmt->execute();
    }
    return false;
  }

  public function _destroy($id)
  {
    $query = "DELETE FROM sessions WHERE id = :id";
    $stmt = $this->db->prepare($query);
    $stmt->bind_param("s", $id);
    return $stmt->execute();
  }

  public function _gc($max)
  {
    $old = time() - $max;
    $query = "DELETE FROM sessions WHERE access < :old";
    $stmt = $this->db->prepare($query);
    $stmt->bind_param("i", $old);
   return  $stmt->execute();
  }

}

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And now the warnings are:
Warning: session_start(): Session callback expects true/false return value in /var/www/vhosts/38999564.servicio-online.net/dev.bodegasferrera.es/admin/emgie/emgieUtils/Session.php on line 64

Warning: session_start(): Failed to read session data: user (path: /opt/alt/php72/var/lib/php/session) in /var/www/vhosts/38999564.servicio-online.net/dev.bodegasferrera.es/admin/emgie/emgieUtils/Session.php on line 64

line 64 is the one in constructor when session_start() is called.

Any idea?

Marco Gasi

ASKER

Okay, here there is the new Session class. I have dropped the external SessionModel and merged the db logic.

<?php

namespace Emgie\EmgieUtils;

require __DIR__ . '/../../vendor/autoload.php';
require_once __DIR__ . '/../../ChromePhp.php';

class Session
{

  private $db;
  private $tableName;

  public function __construct($tableName)
  {
    $database = new DbModel($tableName);
    $this->tableName = $tableName;

    $this->db = $database->getConnection();

    session_set_save_handler(
      array($this, "_open"),
      array($this, "_close"),
      array($this, "_read"),
      array($this, "_write"),
      array($this, "_destroy"),
      array($this, "_gc")
    );
    register_shutdown_function('session_write_close');

    session_start();
  }

  public function _open()
  {
    if (is_null($this->db)) {
      \ChromePhp::log('db in _open is null');
      return false;
    }
    \ChromePhp::log('db in _open is ok');
    return true;
  }

  public function _close()
  {
    $this->db = null;
    return true;
  }

  public function _read($id)
  {
    $query = "SELECT data FROM $this->tableName WHERE id = ?";

    $stmt =  $this->db->stmt_init();
    if ($stmt->prepare($query)) {
      $stmt->bind_param("s", $id);
      $stmt->execute();
      $result = $stmt->get_result();
      $row = $result->fetch_assoc();
      $stmt->close();
      \ChromePhp::log('$row[data]');
      \ChromePhp::log($row['data']);
      if (is_null($row['data'])) {
        return '';
      }
      return $row['data'];
    }
    \ChromePhp::log('_read returns an empty string');
    return '';
  }

  public function _write($id, $data)
  {
    $access = time();
    $query = "REPLACE INTO $this->tableName VALUES (?, ?, ?)";
    $stmt =  $this->db->stmt_init();
    if ($stmt->prepare($query)) {
      $stmt->bind_param("sis", $id, $access, $data);
      return $stmt->execute();
    }
    return false;
  }

  public function _destroy($id)
  {
    $query = "DELETE FROM $this->tableName WHERE id = :id";
    $stmt =  $this->db->stmt_init();
    if ($stmt->prepare($query)) {
      $stmt->bind_param("s", $id);
      return $stmt->execute();
    }
  }

  public function _gc($max)
  {
    $old = time() - $max;
    $query = "DELETE FROM $this->tableName WHERE access < :old";
    $stmt =  $this->db->stmt_init();
    if ($stmt->prepare($query)) {
      $stmt->bind_param("i", $old);
      return  $stmt->execute();
    }
  }
}

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This time it looks to work but not really. when I call session_regenerate_id() I get this error:

Uncaught Error: Failed to open session: user

So the question is now: how to use session_regenerate_id() function when using database to save sessions?

ASKER CERTIFIED SOLUTION

Marco Gasi

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David Favor

You're welcome!