Please Help with Private Endpoint Auth (PHP)

I wonder if someone would be willing to help explain this to me as I've been fighting with it for days... So, I use the premade authentication code from the Wiki (PHP). This function just logs in with Bungie and saves the cookie to a file and return true/false based upon its successful login. I have no idea how to use this function for some reason. Is the bungled value always in this cookie file to pass for the X-CSRF? If so, why does it disappear from this file if the auth function is run more than once? I assume something to do with already being authenticated. Do I need to pass this whole cookie file with each request or just specific information from the file? Like I'm just struggling to figure it all out. How do I get this cookie information and call the private endpoint simultaneously? Bah! I've scored tons of pages/posts in this forum. I've scored the wiki repeatedly. I just can't figure this out. Any help would be so appreciated. Public endpoints are no problem and I can get those parts of my application working. But the private auth just has me baffled.