Function: Checks whether a user is still logged in, for the heartbeat.

Function: Tests if the supplied date is valid for the Gregorian calendar.

Function: Loads the auth check for monitoring whether the user is still logged in.

Function: Outputs the HTML that shows the wp-login dialog when the user is no longer logged in.

Function: Finds hierarchy loops using a callback function that maps object IDs to parent IDs.

Function: Uses the “The Tortoise and the Hare” algorithm to detect loops.

Function: Sends a HTTP header to limit rendering of pages to same origin iframes.