Allow Access to URL from Inside but Not From Internet

Lucas, thanks for the detailed response. Your assumptions are correct. I had seen that post you linked when I was searching and had dismissed it as unrelated to what I was looking for for. I had been lead to believe that the process you just described was sort of automatic, that simply by being in the F5 and using HTTPS that the x509 info would automatically be inserted into the HTTP request header and forwarded to the server.

I thought I was just missing the finer details, but I apparently really am missing the overarching architecture of how this will work! I think the important take away from your code is that I can name the EDIPI whatever I want in the request header. That's enough to let me start writing my PHP. So thanks! 

I think I followed your code fine, but am entirely unfamiliar with the syntax/language. Am I right to assume that my server admins will have access to an F5 console where I'd have to get them to setup rules for how we want our connections to be managed, and the script your provided is an example of one of those handling rules?