Plugin: Upgrade from 3x to 4.1.3

[BosDev]

We've updated our forum to the latest and greatest, and after removing a lot of plugins/products which were ancient, our banner ads disappeared.

The plugin we used to use was:

PHP Code:

ob_start();
include('/home/viperclu/public_html/sponsors/banner-display.php');
$GLOBALS['bannerads'] = ob_get_contents();
ob_end_clean(); 


and then in our header template, we simply added

$GLOBALS['bannerads']

and poof, the ads would appear as we wanted them.

Now, "$GLOBALS['bannerads']" shows up.

I've read a couple threads, but I'm honestly lost here...

Any help would be appreciated.