[Black Snow]

You would just grab the current page URL using something like this:

<?php
$current_page_URL = $_SERVER["SERVER_NAME"] . $_SERVER["REQUEST_URI"]; 
?>

Here $_SERVER["SERVER_NAME"] will give you the doman name of your site and $_SERVER["REQUEST_URI"] will give you the rest.

Example: https://vborg.vbsupport.ru/showthread.php?t=286829

$_SERVER["SERVER_NAME"] will give you vbulletin.org

$_SERVER["REQUEST_URI"] will give you /forum/showthread.php?t=286829

The do a check.

<?php
if {$current_page_URL = xxx} Show banner 1
{else}
Show banner 2
?>