is_user_logged_in()
Function: Determines whether the current visitor is a logged in user.
Source: wp-includes/pluggable.php:1173
is_user_member_of_blog()
Function: Finds out whether a user is a member of a given blog.
Source: wp-includes/user.php:1078
is_user_option_local()
Function: Check whether a usermeta key has to do with the current blog.
Source: wp-includes/ms-deprecated.php:543
is_user_spammy()
Function: Determines whether a user is marked as a spammer, based on user login.
Source: wp-includes/ms-functions.php:2287
is_wp_error()
Function: Checks whether the given variable is a WordPress Error.
Source: wp-includes/load.php:1620
is_wp_version_compatible()
Function: Checks compatibility with the current WordPress version.
Source: wp-includes/functions.php:8565
is_wpmu_sitewide_plugin()
Function: Deprecated functionality for determining if the current plugin is network-only.
Source: wp-admin/includes/ms-deprecated.php:78
is_year()
Function: Determines whether the query is for an existing year archive.
Source: wp-includes/query.php:834
iso8601_timezone_to_offset()
Function: Given an ISO 8601 timezone, returns its UTC offset in seconds.
Source: wp-includes/formatting.php:3674
iso8601_to_datetime()
Function: Given an ISO 8601 (Ymd\TH:i:sO) date, returns a MySQL DateTime (Y-m-d H:i:s) format used by post_date[_gmt].
Source: wp-includes/formatting.php:3696