public function errorExit($header, $url = '', $msgHtml = '')
    {
        $url = htmlspecialchars($url, ENT_QUOTES);
        list(,$h1) = explode(' ', $header, 2);
        $h1 = htmlspecialchars($h1);
        // FastCGI environments require 3rd arg to header() to be set
        list(, $code) = explode(' ', $header, 3);
        header($header, true, $code);
        header('Content-Type: text/html; charset=utf-8');
        echo "<h1>$h1</h1>";
        if ($msgHtml) {
            echo $msgHtml;
        }
        if ($url) {
            echo "<p>Please see <a href='$url'>$url</a>.</p>";
        }
        exit;
    }