官方文档:https://developer.work.weixin.qq.com/document/path/91335
// 授权回调地址,需企业微信设置为可信域名
$callbackUrl = 'https://xxxx';
// 构造网页授权链接,返回 redirect 实例
$redirect = $app->oauth->redirect($callbackUrl);
// 获取url
$targetUrl = $redirect->getTargetUrl();
// 直接跳转
$redirect->send();
// 获取访问用户身份,返回数组格式 $user['UserId']
$code = '回调接收到的code';
$user = $app->oauth->user($code)