WordPress at a glance
function is not described

is_server_error() WP 1.0

No Hooks.

Return

Nothing (null).

Usage

is_server_error ( $sc );

Code of is server error: wp-includes/rss.php VER 5.0.3

<?php
function is_server_error ($sc) {
	return $sc >= 500 && $sc < 600;
}