How to tell if a dynamic sidebar is being displayed on page?

Question

I'm trying to conditionally add a class of has-sidebar to a wrapper div, and I'm struggling to find a conditional statement to see if the sidebar is active on the current page.

For example:

<!-- Open site main wrapper -->
    <div id="site-content" <?php if (is_active_sidebar('sidebar-1')) echo 'class="has-sidebar"' ?>>

The issue is "is_active_sidebar" is always returning true - is there a function or conditional I can check to see if a sidebar is displayed or not?

Answer 1

Because of the way templates are rendered in WordPress it won't be possible to know if a page has a sidebar until after that sidebar has been rendered. This is because code in templates can't 'know' what code exists later in rendering sequence.

What I would recommend is determining what the conditions are which your sidebar is displayed under and using those conditions in your has-sidebar check. For example, if your wrapper opens in header.php but your sidebar is only displayed on posts by rendering it in single.php only, you could check is_single() in header.php to determine whether the sidebar is going to be rendered. You could combine this with is_active_sidebar() if you need to know of the sidebar will have any widgets in it.