通过code 获取openid

 $code = $this->request->post('code');
 $appid = '你的appid';
 $appsecret = '你的secret';
  $weixin = getJson('https://api.weixin.qq.com/sns/jscode2session?appid=' . $appid . '&secret=' . $appsecret . '&js_code=' . $code . '&grant_type=authorization_code');

　　

function getJson($url) {
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $output = curl_exec($ch);
    curl_close($ch);
    return json_decode($output, true);
}