zeichen on "Php code on assigning sidebar on specific pages"

Good day,

I'd like to seek help on the proper coding of the php if condition. I'd like to assign additional pages for the sidebar and the current setup has this line of code:

<?php if($post_name == 'coaching'): ?>

I'd like to know what's the proper code to place if I'd like to add more specific pages for the condition to trigger.

Thanks.