PHP Implementation Example of Session Sharing Using Redis

Preface

For small web services, session data is basically stored locally (more local disk files). However, when multiple services are deployed and session needs to be shared, it is ensured that each service can share the same session data.

redis data is stored in memory, which has good performance and can ensure data integrity with persistence.

Design scheme

1. Implementation by php's own session configuration

#  Use  redis  As a storage scheme 
session.save_handler = redis
session.save_path = "tcp://127.0.0.1:6379"
#  If the connection password is set, ,  The following is used 
session.save_path = "tcp://127.0.0.1:6379?auth= Password "

Test code

<?php
ini_set("session.save_handler", "redis");
ini_set("session.save_path", "tcp://127.0.0.1:6379");

session_start();
echo "<pre>";
$_SESSION['usertest'.rand(1,5)]=1;
var_dump($_SESSION);

echo "</pre>";

Output ↓

array(2) {
["usertest1"]= >
int(88)
["usertest3"]= >
int(1)
}
usertest1|i:1;usertest3|i:1;

Evaluation

Advantages: Simple implementation, no need to modify php code Disadvantages: Configuration does not support diversification and can only be applied to simple scenarios

2. Set up user-defined session store functions

The user-defined session function is set through the session_set_save_handler () function.

session_set_save_handler ( callable $open , callable $close , callable $read , callable $write , callable $destroy , callable $gc [, callable $create_sid [, callable $validate_sid [, callable $update_timestamp ]]] ) : bool
  
# >= php5.4
session_set_save_handler ( object $sessionhandler [, bool $register_shutdown = TRUE ] ) : bool

After configuring the session store function, execute session_start ().

The specific code is omitted. One copy of Memcached (from Symfony framework code) is provided below:

<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\HttpFoundation\Session\Storage\Handler;

/**
 * MemcacheSessionHandler.
 *
 * @author Drak <drak@zikula.org>
 */
class MemcacheSessionHandler implements \SessionHandlerInterface
{
  /**
   * @var \Memcache Memcache driver.
   */
  private $memcache;

  /**
   * @var int Time to live in seconds
   */
  private $ttl;

  /**
   * @var string Key prefix for shared environments.
   */
  private $prefix;

  /**
   * Constructor.
   *
   * List of available options:
   * * prefix: The prefix to use for the memcache keys in order to avoid collision
   * * expiretime: The time to live in seconds
   *
   * @param \Memcache $memcache A \Memcache instance
   * @param array   $options An associative array of Memcache options
   *
   * @throws \InvalidArgumentException When unsupported options are passed
   */
  public function __construct(\Memcache $memcache, array $options = array())
  {
    if ($diff = array_diff(array_keys($options), array('prefix', 'expiretime'))) {
      throw new \InvalidArgumentException(sprintf(
        'The following options are not supported "%s"', implode(', ', $diff)
      ));
    }

    $this->memcache = $memcache;
    $this->ttl = isset($options['expiretime']) ? (int) $options['expiretime'] : 86400;
    $this->prefix = isset($options['prefix']) ? $options['prefix'] : 'sf2s';
  }

  /**
   * {@inheritdoc}
   */
  public function open($savePath, $sessionName)
  {
    return true;
  }

  /**
   * {@inheritdoc}
   */
  public function close()
  {
    return $this->memcache->close();
  }

  /**
   * {@inheritdoc}
   */
  public function read($sessionId)
  {
    return $this->memcache->get($this->prefix.$sessionId) ?: '';
  }

  /**
   * {@inheritdoc}
   */
  public function write($sessionId, $data)
  {
    return $this->memcache->set($this->prefix.$sessionId, $data, 0, time() + $this->ttl);
  }

  /**
   * {@inheritdoc}
   */
  public function destroy($sessionId)
  {
    return $this->memcache->delete($this->prefix.$sessionId);
  }

  /**
   * {@inheritdoc}
   */
  public function gc($maxlifetime)
  {
    // not required here because memcache will auto expire the records anyhow.
    return true;
  }

  /**
   * Return a Memcache instance
   *
   * @return \Memcache
   */
  protected function getMemcache()
  {
    return $this->memcache;
  }
}