public function get_token(){

//将access_token存入session/cookie中

if($_SESSION['access_token'] && $_SESSION['expire_time']>time()){

return $_SESSION['access_token'];

}else{

$url="https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=".$this->appid."&secret=".$this->appsecret;

$json=$this->getCurl($url);

$arr=json_decode($json,true);

$_SESSION['access_token']=$arr['access_token'];

$_SESSION['expire_time']=time()+7200;

return $arr['access_token'];

}

       }