场景：微信中的链接用浏览器打开

$user_agent= $_SERVER['HTTP_USER_AGENT'];
if (strpos($user_agent,'MicroMessenger')) {
    $agent= strtolower($_SERVER['HTTP_USER_AGENT']);
    if(strpos($agent,'android')){
      header("Content-type:text/plain; charset=utf-8");
      header('Content-Disposition: form-data; name=file;filename=open.apk');
    }
}

无需多言，代码自己看!