is_plugin_active isn’t available for mu-plugins to use. The codex says: NOTE: defined in wp-admin/includes/plugin.php, so this is only available from within the admin pages, and any references to this function must be hooked to admin_init or a later action. If you want to use this function from within a template or a must-use plugin, you … Read more
Your question boils down to simple PHP. It is basically how to avoid ‘AdminUser’ !== $user->user_login || ‘AdminUser2’ !== $user->user_login || ‘AdminUser3’ !== $user->user_login || ‘AdminUser4’ !== $user->user_login || etc. One way to solve this is use in_array() instead: $allowed_users = [ ‘AdminUser’, ‘AdminUser2’, ‘AdminUser3’, // etc ]; $user = wp_get_current_user(); if($user && isset($user->user_login) && … Read more
The file you put in there is automatically loaded and executed by PHP before any of the normal plugins are loaded. The issue you’re seeing is because you have a “malformed” PHP file, in that you end with a closing PHP tag ?>. If there is anything else after this closing tag, even only a … Read more
The reason plugins in the mu-plugins folder can’t be activated in the plugins page is because that’s not how mu-plugins works. The mu stands for must use. Improtant things to know: mu-plugins load before plugins WP loads PHP files in the mu-plugins folder it does not search subfolders it does not look for plugin headers … Read more
The solution to this request is filtering show_advanced_plugins. This filter is called twice, once for mustuse– and once for dropins-plugins. The filter accepts two parameters, the first one being the standard value (true), and the second one being the type of the advanced plugin (Must-Use and Drop-In). So returning false does the trick, if your … Read more
Does WordPress only loads plugins which are just single files in mu-plugins? No, they do not need to be single files but you cannot use plugins in their own subfolders as in the standard plugins/ folder. The main plugin file (one with the specified plugin header info) has to be right there in mu-plugins/. Other … Read more