Using WordPress ‘is_main_site()’ PHP function
Determines whether a site is the main site of the current network.
PHP
Using WordPress ‘is_main_query()’ PHP function
The `is_main_query()` function in WordPress is used to determine if a query is the main query, which can be useful for modifying or excluding certain queries
Using WordPress ‘is_main_network()’ PHP function
Determines whether a network is the main network of the Multisite installation.
Using WordPress ‘is_main_blog()’ PHP function
Deprecated functionality to determin if the current site is the main site.
Using WordPress ‘is_local_attachment()’ PHP function
Determines whether an attachment URI is local and really an attachment.
Using WordPress ‘is_login()’ PHP function
Determines whether the current request is for the login screen.
Using WordPress ‘is_locale_switched()’ PHP function
Is_locale_switched() is a useful WordPress function that allows you to check whether the locale has been switched or not
Using WordPress ‘is_lighttpd_before_150()’ PHP function
Determines whether the server is running an earlier than 1.5.0 version of lighttpd.
Using WordPress ‘is_active_sidebar()’ PHP function
The `is_active_sidebar()` function in WordPress checks if a sidebar contains widgets and returns true if it does, allowing you to conditionally display its contents