Using WordPress ‘get_theme_update_available()’ PHP function
Retrieves the update link if there is a theme update available.
HTTPS
Using WordPress ‘is_local_attachment()’ PHP function
Determines whether an attachment URI is local and really an attachment.
Using WordPress ‘iso8601_timezone_to_offset()’ PHP function
Given an ISO 8601 timezone, returns its UTC offset in seconds.
Using WordPress ‘install_network()’ PHP function
The `install_network()` function in WordPress is used to install a new network for a WordPress multisite installation