PHP Showing different files when switching from HTTP to HTTPS

this is my first time asking here I hope somebody can help me.

I'm working on an application that requires to switch 开发者_运维技巧from HTTP to HTTPS when the user is going to check out. I'm using Smarty. The problem comes when I redirect from using this:

if I do a die() it shows the URL with HTTPS but when I redirect it shows a different file (From Smarty) but if I change HTTPS to HTTP and redirect, it works...

Can somebody help me? I'm lost and I have been trying for days!

Thanks