PHP共享内存yac操作类

<?php

/**
 * 进程间共享内存操作类
 */
class Pshmop
{
    protected static $_models = array();
    private $_yac = null;
    private static $_keyPrefix = 'shm_';
    private static $_ttlMaxTime = 7776000;  //86400*90 为防止永久贮存及保存时间过久造成内存消耗严重导致数据被踢出

/**
     * Returns the static model of the specified AR class.
     * @param string $className active record class name.
     * @return Order the static model class
     */
    public static function model($className = __CLASS__)
    {
        $model = null;
        if (isset(self::$_models[$className]))
            $model = self::$_models[$className];
        else {
            $model = self::$_models[$className] = new $className(null);
        }
        return $model;
    }

public function __construct() {
        if(extension_loaded("yac")){
            $this->_yac = new Yac(self::$_keyPrefix);
        }
    }

/**
    * add value
    * @param mixed $keys
    * @param mixed $value
    * @param int $ttl
    * @return mixed
    */
    public function add($key, $value, $ttl=-1){
        if(empty($key)){
            return null;
        }

if(empty($this->_yac)){
            return null;
        }

if($ttl<0 || $ttl>self::$_ttlMaxTime){
            $ttl = self::$_ttlMaxTime;
        }

return $this->_yac->add($key, $value, $ttl);
    }

/**
    * set value
    * @param mixed $keys
    * @param mixed $value
    * @param int $ttl
    * @return mixed
    */
    public function set($key, $value, $ttl=-1){
        if(empty($key)){
            return null;
        }

if(empty($this->_yac)){
            return null;
        }

if($ttl<0 || $ttl>self::$_ttlMaxTime){
            $ttl = self::$_ttlMaxTime;
        }

return $this->_yac->set($key, $value, $ttl);
    }

/**
    * get value
    * @param mixed $keys
    * @return mixed
    */
    public function get($key){
        if(empty($key)){
            return null;
        }

if(empty($this->_yac)){
            return null;
        }

return $this->_yac->get($key);
    }

/**
    * delete key
    * @param mixed $keys
    * @param int $delay
    * @return mixed
    */
    public function delete($key, $delay=0){
        if(empty($key)){
            return null;
        }

if(empty($this->_yac)){
            return null;
        }

return $this->_yac->delete($key, $delay);
    }

/**
    * flush shm
    * @param void
    * @return mixed
    */
    public function flush(){

if(empty($this->_yac)){
            return null;
        }

return $this->_yac->flush();
    }

/**
    * get shm info
    * @param void
    * @return mixed
    */
    public function info(){

if(empty($this->_yac)){
            return null;
        }

return $this->_yac->info();
    }

}