app\models\Invitation::getLink PHP Method

    public function getLink($type = 'view', $forceOnsite = false)
    {
        if (!$this->account) {
            $this->load('account');
        }
        $url = trim(SITE_URL, '/');
        $iframe_url = $this->account->iframe_url;
        if ($this->account->hasFeature(FEATURE_CUSTOM_URL)) {
            if ($iframe_url && !$forceOnsite) {
                return "{$iframe_url}?{$this->invitation_key}";
            } elseif ($this->account->subdomain) {
                $url = Utils::replaceSubdomain($url, $this->account->subdomain);
            }
        }
        return "{$url}/{$type}/{$this->invitation_key}";
    }

 public function transform(Invitation $invitation)
 {
     return ['id' => (int) $invitation->public_id, 'key' => $invitation->getName(), 'status' => $invitation->getStatus(), 'link' => $invitation->getLink(), 'sent_date' => $invitation->sent_date, 'viewed_date' => $invitation->sent_date];
 }