PHP使用Redis实现Session共享的实现示例

前言

小型web服务, session数据基本是保存在本地(更多是本地磁盘文件), 但是当部署多台服务, 且需要共享session, 确保每个服务都能共享到同一份session数据.

redis 数据存储在内存中, 性能好, 配合持久化可确保数据完整.

设计方案

1. 通过php自身session配置实现

# 使用 redis 作为存储方案
session.save_handler = redis
session.save_path = "tcp://127.0.0.1:6379"
# 若设置了连接密码, 则使用如下
session.save_path = "tcp://127.0.0.1:6379?auth=密码"

测试代码

<?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>";

输出 ↓

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

评价

• 优点: 实现简单, 无需修改php代码
• 缺点: 配置不支持多样化, 只能应用于简单场景

2. 设置用户自定义会话存储函数

通过 session_set_save_handler() 函数设置用户自定义会话函数.

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

在配置完会话存储函数后, 再执行 session_start() 即可.

具体代码略, 以下提供一份 Memcached 的(来自Symfony框架代码):

<?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 SymfonyComponentHttpFoundationSessionStorageHandler;

/**
 * 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;
  }
}

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