wp_set_post_categories assumes $post_categories has a value in [0], but wp_insert_post doesn't assign the default category there

[jorbin]

right now wp_insert post assigns the default category to a post just as an array item which should be in the 0 ofset. However this isn't guaranteed. If we cast it as the 0 offset in wp_insert_post, this solves the problem

To reproduce:

on a vanilla install with wp_debug enabled, add a post modifying the categories. This causes the following error: Notice: Undefined offset: 0 in /opt/lampp/htdocs/amun/wp/trunk/wp-includes/post.php on line 2561

My first patch didn't solve it. For the second I added a check to make sure we have a category assigned in [0] if there is only one category.

I wasn't able to reproduce the notice. Could you provide more detailed steps to reproduce?

Anyway, 14438.diff:

• removes duplicated validation code from wp_insert_post()
• uses reset($post_category) instead of $post_category[0]

Replying to scribu:

I wasn't able to reproduce the notice. Could you provide more detailed steps to reproduce?

I get the error when only one category is checked before clicking Update

Undefined offset: 0 in \wp-dev\wp-includes\post.php on line 2574

(In [14447]) use reset vs offset 0, props scribu, see #13246

Fixed. Thanks scribu and wpmuguru

#5096 was marked as a duplicate.