Warning: join() [function.join]:

Hello t0symmonds I have exactly the same problem.

Anyone a solution?

Same problem here. It’s appearing on every page.

I got the error message to go away by changing line 296 in post-template.php to

if (get_post_class( $class, $post_id) != '') {
	   echo 'class="' . join( ' ', get_post_class( $class, $post_id ) ) . '"';
	}

Not sure if it’s the best fix, but is working for now.

Thanks Snegu

Where do I find post-template.php?

Snegu –
Thank you for the fix, it worked for me. Would you mind explaining what I just did? Messing with core WP files scares the !&#* out of me, so maybe you could reassure me a bit? Thanks again!

If should be scarry, taliwait, cause you don’t fix anything by doing this. Next update and you’ll be again with the same message.

Suppressing errors is done by adding this to the last line of wp-config.php:

error_reporting(0);

This doesn’t fix the problem either, but at least it hides it from the visitors of the site.