Using WordPress ‘register_sidebar()’ PHP function
Builds the definition for a single sidebar and returns the ID.
WordPress
Using WordPress ‘register_post_status()’ PHP function
Learn how to use the WordPress'register_post_status()' function to create or modify custom post statuses with various options such as labels, dates, visibility,…
Using WordPress ‘register_meta()’ PHP function
Learn how to use the WordPress'register_meta()' function to register custom meta keys for your website
Using WordPress ‘register_deactivation_hook()’ PHP function
Learn how to use the WordPress'register_deactivation_hook()' function to set a deactivation hook for your plugins in this comprehensive article