PHP in vB 3.8.6 Templates

[grayloon]

I need to use a bit of PHP code in my vBulletin 3.8.6 header template. I tried following the instructions in the docs, but it's not working.

I created an external PHP file at the root of my forums called realtree-nav.php.

I created a plugin with the following contents:

PHP Code:

ob_start();
include('realtree-nav.php');
$includedphp = ob_get_contents();
ob_end_clean(); 


In AdminCP > Styles & Templates > Default > header, I added the following:

{vb:raw includedphp}

In my forums, {vb:raw includedphp} shows up without being parsed. What have I done wrong?