ms_allowed_http_request_hosts() WordPress Function

function ms_allowed_http_request_hosts( $is_external, $host ) {
	global $wpdb;
	static $queried = array();
	if ( $is_external ) {
		return $is_external;
	}
	if ( get_network()->domain === $host ) {
		return true;
	}
	if ( isset( $queried[ $host ] ) ) {
		return $queried[ $host ];
	}
	$queried[ $host ] = (bool) $wpdb->get_var( $wpdb->prepare( "SELECT domain FROM $wpdb->blogs WHERE domain = %s LIMIT 1", $host ) );
	return $queried[ $host ];
}
Uses	Description
wp-includes/ms-network.php:get_network()	Retrieves network data given a network ID or network object.
wp-includes/wp-db.php:wpdb::get_var()	Retrieves one variable from the database.
wp-includes/wp-db.php:wpdb::prepare()	Prepares a SQL query for safe execution.