Method getTrackingLink

// Tracking
public static function getTrackingLink($common)
{
    $trackingLink = '';
    if (isset($common->tracking_link_custom) && $common->tracking_link_custom != '') {
        $trackingLink = '<a href="' . $common->tracking_link_custom . '">' . $common->tracking_link_custom . '</a>';
    } else {
        if (isset($common->shippingtrackinglink) && $common->shippingtrackinglink != '' && isset($common->tracking_number) && $common->tracking_number != '') {
            $trackingLink = '<a href="' . $common->shippingtrackinglink . $common->tracking_number . '">' . $common->shippingtrackinglink . $common->tracking_number . '</a>';
        }
    }
    return $trackingLink;
}