WordPress at a glance
function is not described

WP_Site::__isset() public WP 4.6.0

Isset-er.

Allows current multisite naming conventions when checking for properties. Checks for extended site properties.

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

No Hooks.

Return

true|false. Whether the property is set.

Usage

$WP_Site = new WP_Site();
$WP_Site->__isset( $key );
$key(string) (required)
Property to check if set.

Changelog

Since 4.6.0 Introduced.

Code of WP_Site::__isset() WP 5.7.2

<?php
public function __isset( $key ) {
	switch ( $key ) {
		case 'id':
		case 'network_id':
			return true;
		case 'blogname':
		case 'siteurl':
		case 'post_count':
		case 'home':
			if ( ! did_action( 'ms_loaded' ) ) {
				return false;
			}
			return true;
		default: // Custom properties added by 'site_details' filter.
			if ( ! did_action( 'ms_loaded' ) ) {
				return false;
			}

			$details = $this->get_details();
			if ( isset( $details->$key ) ) {
				return true;
			}
	}

	return false;
}