将Session写入Memcache

通过session_set_save_handler()方法自定义Session写入Memcache

 <?php
     class MemSession{
         private static $handler = null;
         private static $lifetime = null;
         private static $time = null;
         const MS = 'session';

         private static function init($handler){
             self::$handler = $handler;
             self::$lifetime = ini_get('session.gc_maxlifetime');
             self::$time = time();
         }

         public static function start($memcache){
             self::init($memcache);
             //调用类中的方法要用数组,__CLASS__代表本类
             session_set_save_handler(
                 array(__CLASS__,'open'),
                 array(__CLASS__,'close'),
                 array(__CLASS__,'read'),
                 array(__CLASS__,'write'),
                 array(__CLASS__,'destroy'),
                 array(__CLASS__,'gc')
             );
             session_start();
         }

         public static function open($path,$name){

         }
         public static function close(){

         }

         public static function read($PHPSESSID){
             $val = self::$handler->get(self::session_key($PHPSESSID));

             if($val===false || $val==null){
                 return false;
             }
             return $val;
         }
         public static function write($PHPSESSID,$data){
             $method = $data? 'set':'replace';
             return self::$handler->$method(self::session_key($PHPSESSID),$data,MEMCACHE_COMPRESSED,self::$lifetime);
         }

         public static function destroy($PHPSESSID){
             return self::$handle->delete(self::session_key($PHPSESSID));
         }
         //memcache本身就有限定时间，数据自动销毁，所以可不使用gc方法
         public static function gc($lifetime){
             return true;
         }

         //给sessionID加前缀，避免key重复
         private static function session_key($PHPSESSID){
             $session_key = self::MS.$PHPSESSID;
             return $session_key;
         }
     }
     $mem = new Memcache;
     $mem->connect("localhost",11211) or die("could not connect");
     MemSession::start($mem);