Symfony\Component\HttpFoundation\Request::getScheme PHP Method

    public function getScheme()
    {
        return $this->isSecure() ? 'https' : 'http';
    }

 public function serialize(JsonSerializationVisitor $visitor, OwnerData $owner, array $type)
 {
     $scheme = $this->request->getScheme() . '://' . $this->request->getHttpHost();
     $data = $owner->getData();
     if ($owner->getAvatarFileName()) {
         $data['avatar_file_path'] = $this->uh->asset($owner, 'avatar');
     } else {
         $data['avatar_file_path'] = $scheme . $owner->getDefaultAvatar();
     }
     return $data;
 }