WordPress Version: 4.6
/**
* Sends a Link: rel=shortlink header if a shortlink is defined for the current page.
*
* Attached to the {@see 'wp'} action.
*
* @since 3.0.0
*/
function wp_shortlink_header()
{
if (headers_sent()) {
return;
}
$shortlink = wp_get_shortlink(0, 'query');
if (empty($shortlink)) {
return;
}
header('Link: <' . $shortlink . '>; rel=shortlink', false);
}