Adding PHP function to IPS theme

[Zennuie]

Does anyone have any experience regarding adding PHP to a theme?
I was trying to add the code to my theme in either the globalTemplate or navbar section. I was getting an error when doing so, I tried using the double curly brackets; but this caused the same error. 

If anyone could help with this matter, it would be a life saver!

<?php if (isset($_SERVER['HTTP_CF_CONNECTING_IP'])) $_SERVER['REMOTE_ADDR'] = $_SERVER['HTTP_CF_CONNECTING_IP'];?>

[opentype]

You need to use the template syntax as explained here on several pages. 
https://invisioncommunity.com/4guides/themes-and-customizations/template-syntax/introduction-to-template-syntax-r137/

 

[Stuart Silvester]

It's also worth pointing out that the code you're trying to use, you don't need to use.

Make sure you have enabled the 'Trust IP addresses provided by proxies?' setting in your AdminCP.