PDOHelper (原创)

class PDOHelper{
        public static $db =null;// new PDO('mysql:host=192.168.1.68;dbname=test','root','123456'); 

        public static function  _connect(){
                try {
                        if(!isset($db)){
                                self::$db= new PDO('mysql:host=192.168.1.68;dbname=test','root','123456');
                                self::$db->query("SET NAMES 'utf8';");
                        }
                } catch (PDOException $e) {
                        throw new Exception($e->getMessage(), $e->getCode());
                }
        }

        public static function query($sql,$returnAffectCount=false){
                self::_connect();
                $st = self::$db->query($sql);

                if(false===$st){
                        $rs=false;
                }else if($returnAffectCount){
                        $rs=$st->rowCount();
                }else{
                        $st->setFetchMode(PDO::FETCH_ASSOC);
                        $rs=$st->fetchAll();
                }
                return $rs;
        }

        public static  function exec($sql){
                self::_connect();
                $count =self::$db->exec($sql);
                return $count;
        }

}