获得accesstoken的方法

public function getAccessToken()
{
   $accesstokenTable= M('weixin_accesstoken')->find();
   if($accesstokenTable==false||$accesstokenTable['time']+7000<time())
   {
      $appid=M('weixin_appid')->find();
      $wxurl='https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid='.$appid['appid'].'&secret='.$appid['secret'];
      $result=$this->https_request($wxurl,null);
      $arr=json_decode($result,true);
      $accesstoken=$arr['access_token'];
      $time=time();
      $data=array();
      $data['appid']=$appid['appid'];
      $data['accesstoken']=$accesstoken;
      $data['time']=$time;
      M('weixin_accesstoken')->add($data);
   }else{
      $accesstoken=$accesstokenTable['accesstoken'];
   }
   return $accesstoken;
}
public function https_request($url,$data = null){
   $curl = curl_init();
   curl_setopt($curl, CURLOPT_URL, $url);
   curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, FALSE);
   curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, FALSE);
   if (!empty($data)){
      curl_setopt($curl, CURLOPT_POST, 1);
      curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
   }
   curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
   $output = curl_exec($curl);
   curl_close($curl);
   return $output;
}