使用C＃从文件调用特定的PHP函数

Question

I wrote a simple script in c# to connect to run a PHP file from my website. I'm curious if there could be a simple way to call a PHP function from that file like,

function start() {
  HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://localhost/ext_connect_sql/requestlogin.php");
}