[moonray]

FINAL WORKING CODE:

Product: vBulletin
Title: Insert Simple PHP
Execution order: 5
Hook Location: global_start
PHP code:

ob_start();
include('simple.php');
$simple_php = ob_get_contents();
ob_end_clean();

vB_Template::preRegister('navbar',array('simple_php' => $simple_php));

Plugin is active: Yes

Now, go to the NAVBAR template and insert

{vb:raw insert_simple_php}

just under the code

{vb:raw ad_location.global_below_navbar}