public static function getHeader()
{
$output = '';
foreach (self::$classes as $class) {
$link = $class->getHeaderLink();
if ($link) {
$output .= ' <link rel="alternate" title="' . $class->title . ' - ' . $class->description . '" href="' . htmlspecialchars($link['url']) . '" type="' . $link['type'] . '">' . "\n";
}
}
return $output;
}