Using PHP code to display banners must use 'print' and not 'return'

The INSTALL file has comprehensive instructions on how to setup the ad system.

One thing is obsolete though and needs to be updated: the PHP code that needs to be included in node and/or blocks to display an add.

It currently says

return banner_display();

Because in 4.5.x Drupal's theme system was changed, this should instead be as follows:

print banner_display();