详细教程见
https://blog.youkuaiyun.com/etongs/article/details/73327507
phpCAS::client(CAS_VERSION_2_0, ‘ssaao.aaaaaaa.com’,443,"");
//phpCAS::client(CAS_VERSION_2_0, $cas_host, $cas_port, $cas_context);
$cas_host: 公司OA 入口地址
$cas_port: php server 端口号
$cas_context: 用“”