WordPress at a glance
function is not described

WP_User::exists() public WP 3.4.0

Determine whether the user exists in the database.

{} It's a method of the class: WP_User{}

No Hooks.

Return

true|false. True if user exists in the database, false if not.

Usage

$WP_User = new WP_User();
$WP_User->exists();

Changelog

Since 3.4.0 Introduced.

Code of WP_User::exists() WP 5.7

<?php
public function exists() {
	return ! empty( $this->ID );
}