Updating Co-Authors Plus to v2.6.1 has triggered a conflict with the More Taxonomies v1.1 plugin, littering my site’s pages with dozens of instances of this error message:
Warning: call_user_func_array() expects parameter 1 to be a valid callback, first array member is not a valid class name or object in /home/ucbnews/sandbox/wp-includes/plugin.php on line 170
I realize that More Taxonomies has not been updated in months, and that comments in their forum indicate it is not a cleanly coded plugin. Still, CAP and MT played nicely with each other on my site until the latest CAP update. And both of them provide important functionality to my site, so before I could remove one I’d have to find an alternative way to provide the same function. Any easy suggestions on how to restore harmony to the neighborhood?
OK, I actually managed to find a fix already. More Taxonomies was easier to reverse engineer, and it appears to deserve more blame than Co-Authors Plus. It’s running a function called set_default_data at a priority of 1, which seems to be collecting custom taxonomies, but somehow clobbering the co-author ones. If you set its run priority to run later, the issue goes away.
So open up more-taxonomies-object.php in the More Taxonomies plugin folder, and edit line 10, from: