What is mean this error when I click “Categories” (URL: /wp-admin/edit-tags.php?taxonomy=category):
“Fatal error: Call to undefined function filter_var() in /home/host/site.com/docs/wp-content/plugins/advanced-custom-fields/core/controllers/everything_fields.php on line 266”?
the filter_var function is a core PHP function since 5.2
Perhaps you are running an older version of PHP?
I’ll take a look at the core of WP and see what I can use for better compatibility with old PHP versions.
For now, you can either modify the core code or upgrade your PHP version
I don`t know, but server reply: “Apache/1.3.42 (Unix) PHP/5.3.13″… maybe the reason something else?
Would you mind contacting your host and asking them why you are seeing this error?