function test_header_status_string_works_with_many_status()
 {
     $this->assertEquals("HTTP/1.1 200 OK", No2_HTTP::header_status_string(200));
     $this->assertEquals("HTTP/1.1 303 See Other", No2_HTTP::header_status_string(303));
     $this->assertEquals("HTTP/1.1 403 Forbidden", No2_HTTP::header_status_string(403));
     $this->assertEquals("HTTP/1.1 404 Not Found", No2_HTTP::header_status_string(404));
     $this->assertEquals("HTTP/1.1 500 Internal Server Error", No2_HTTP::header_status_string(500));
 }
<?php

/*
 * some expected error status code have a more userfriendly message than the raw HTTP reason
 * phrase.
 */
$status = $this->status();
switch ($status) {
    case No2_HTTP::NOT_FOUND:
        $message = t('404 Page not found.');
        break;
    case No2_HTTP::UNAUTHORIZED:
        $message = t('You are not authorized to access this page.');
        break;
    default:
        $http_status_string = No2_HTTP::header_status_string($status);
        if (!is_null($http_status_string)) {
            $message = preg_replace('/HTTP\\/\\d+\\.\\d+\\s*/', '', $http_status_string);
        } else {
            $message = "An error occured.";
        }
}
?>

<h1><?php 
print t('Oups!');
?>
</h1>
<p><?php 
print h($message);
?>
    /**
     * A very simple error page.
     *
     * This method is intended to be overrided by subclass to handle errors in
     * a more friendly way.
     */
    protected function render_error()
    {
        $http_status_string = No2_HTTP::header_status_string($this->status());
        if (!is_null($http_status_string)) {
            $message = preg_replace('/HTTP\\/\\d+\\.\\d+\\s*/', '', $http_status_string);
        } else {
            $message = "An error occured.";
        }
        ?>
        <html>
            <head><title><?php 
        print h($message);
        ?>
</title></head>
            <body>
                <h1>Error: <?php 
        print h($message);
        ?>
</h1>
            </body>
        </html>
        <?php 
    }