Building Twilio Phone Company Directory

I'm trying to implement the following tutorial from Twilio:

https://www.twilio.com/docs/tutorials/companydirectory

I'm currently stuck at the following step:

You would assign this scripts URL to your incoming phone number in Twilio. When a call is received at that phone number, Twilio makes a request to this script.

How can I make a PHP file available for execution online so that Twilio can make a request to this file?

Thanks, Eyad