$user_agent = $_SERVER['HTTP_USER_AGENT'];

if (strpos($user_agent, 'MicroMessenger') === false) {

    // 非微信浏览器禁止浏览

    echo "HTTP/1.1 401 Unauthorized";

} else {

    // 微信浏览器，允许访问

    echo "MicroMessenger";

    // 获取版本号

    preg_match('/.*?(MicroMessenger\/([0-9.]+))\s*/', $user_agent, $matches);

    echo '<br>Version:'.$matches[2];

}