http://phpmaster.com/saving-php-sessions-in-redis/

RedisSessionHandler.php

<?php
class RedisSessionHandler implements \SessionHandlerInterface{

	public $ttl = 1800; // 30 minutes default
	protected $db;
	protected $prefix;

	
	public function __construct(Predis\Client $db, $prefix = 'PHPSESSID:') {

		$this->db = $db;

		$this->prefix = $prefix;

	}

	public function open($savePath, $sessionName) {

		// No action necessary because connection is injected

		// in constructor and arguments are not applicable.

	}
	
	public function close() {

		$this->db = null;
		unset($this->db);

	}

	public function read($id) {
		$id = $this->prefix . $id;
		$sessData = $this->db->get($id);
		$this->db->expire($id, $this->ttl);
		return $sessData;
	}

	public function write($id, $data) {
		$id = $this->prefix . $id;
		$this->db->set($id, $data);
		$this->db->expire($id, $this->ttl);
	}

	public function destroy($id) {
		$this->db->del($this->prefix . $id);
	}

	public function gc($maxLifetime) {
		// no action necessary because using EXPIRE
	}
}