"Fatal error: [] operator not supported for strings in wp-includes/classes.php on line 402" after upgrade to 2.1

[gregh]

I just performed an upgrade to 2.1 and when I try to go to "Admin -> Manage -> Posts" I get the following error:

"Fatal error: [] operator not supported for strings in /path_to_wp/wp-includes/classes.php on line 402"

The last thing printed to the browser prior to the error was "Browse category:", the rest of the page is blank. This makes managing posts impossible, so it is a pretty big deal.

So it seems that the minimum PHP version requirement was bumped in this release but the release notes don't mention this at all. So this either WordPress itself or the release notes need to be fixed.

For reference, I am running Red Hat Enterprise Linux (ES3), and the latest version of PHP supplied by Red Hat (with backported security patches) is PHP 4.3.2. The only active plugin is Akismet.

[ryan]

The required PHP ersion vhas not been bumped. For some reason, Walker::walk() is being passed a string instead of an array.

[markjaquith]

Tracing this backwards, I've gotten this far:

category-template.php:182 must be returning non-array

$categories = get_categories($r);

So the bug is probably there. get_categories should probably return blank array() if it has no results.

[charleshooper]

I can't reproduce this but I decided to poke around and take a look anyways. get_categories() actually DOES return a blank array if it doesn't have any resultsp

        if ( empty($categories) )
                return array();

I can't really figure out how or why Walker:walk() is being passed a string instead of an array, but if we can get rid of that ugly fatal error then we can at least get our users able to manage their posts.

[markjaquith]

99% sure this was being caused by the bug fixed here. [4856] [4857]

A definite symptom of the bug was get_categories() returning a blank string.

[gregh]

Would you like me to test whether these fixes have any impact?

Should I try out walk_array_check.diff, or the fixes from changesets [4856] and [4857], or both?

My understanding is that those changesets should be enough, right?

[foolswisdom]

gregh, it would be awesome if you can try the changeset for your version either 2.1 or trunk. Sounds like that should be enough.

[gregh]

Ok, I tried the changeset for the 2.1 branch [4857] and can confirm that the error has gone away.