简单的redis单例类

/*
自己写着玩
*/
<?php
class redis
{
    const REDISHOST = '127.0.0.1';
    const REDISPORT = '6379';
    const REDISPASWORD = '';
    const REDISDBNAME = 0;
    private static $_obj = null;
    private function __construct(){
    }
    private function __clone(){}//禁止克隆
    private  static function connect_redis($dbname = null)
    {
        try{
            self::$_obj = new redis();
            self::$_obj->connect(self::REDISHOST,self::REDISPORT);
            if(self::REDISPASWORD){
                self::$_obj->auth(self::REDISPASWORD);
            }
            if($dbname){
                $dbname = (int)$dbname;
                self::$_obj->select($dbname);
            }else{
                self::$_obj->select(self::REDISDBNAME);
            }
        }catch (Exception $e){
            exit($e->getMessage().'<br/>');
        }
        return self::$_obj;
    }
    public static function getRedis()
    {
        if(!self::$_obj){
            self::$_obj = self::connect_redis();
        }
        return self::$_obj;
    }
    public function set($key,$value)
    {
        if(!empty($key) && !empty($value)){
            return self::$_obj->set($key,$value);
        }else{
            return false;
        }
    }
    public function get($key)
    {
        if(!empty($key)){
            return self::$_obj->get($key);
        }else{
            return false;
        }
    }
    public function exists($key)
    {
        if(!empty($key)){
            return self::$_obj->exists($key);
        }else{
            return false;
        }
    }
}
//直接调用getredis
$redis =  redis::getredis();
$redis->get('a');