WordPress Version: 4.6
/**
* Injects rel=shortlink into the head if a shortlink is defined for the current page.
*
* Attached to the {@see 'wp_head'} action.
*
* @since 3.0.0
*/
function wp_shortlink_wp_head()
{
$shortlink = wp_get_shortlink(0, 'query');
if (empty($shortlink)) {
return;
}
echo "<link rel='shortlink' href='" . esc_url($shortlink) . "' />\n";
}