Hey,
I noticed the same thing with custom taxonomies. I looked into this problem and got it working again for custom taxonomies, the same fix should work for categories (but you will need to test).
This is what happened:
WordPress changed the way that the term_exists() function works. In particular the default has been changed from 0 to null. What this means is that if you pass in 0 the behavior is now different and it will look for the parent with id = 0. (changing behavior of inputs is generally a nono as it will break code that relies on stuff like this :/)
See:
https://core.trac.wordpress.org/ticket/29851
In this plugin it relies on the fact that the 0 will bypass checking for the parent. When a 0 is passed in now it checks to see if there is a child matching with a parent of id = 0.
This is the fix that I added, it hasn’t been heavily tested but works in the scenario that I am using.
For the following line in create_terms():
$child_info = $this->term_exists($child, $taxonomy, $parent_id);
I replaced that line with the following:
if ($parent_id === 0) {
$child_info = $this->term_exists($child, $taxonomy, null);
}
else {
$child_info = $this->term_exists($child, $taxonomy, $parent_id);
}
There is some code below that relies on the fact that the $parent_id is 0. so changing the $parent_id to null when no parent is found will cause some side effects.
Please note that the term-exists() function is overridden in the file so removing the $parent_id from the term-exists() function call will cause it to be set to 0 and give the same incorrect response.
Hope this helps diagnose for anyone having this issue because at the moment child categories and child taxonomies won’t work with the 0 or empty i.e. “0,cat” like it used to.
Thanks,
Scott
