// release frequency
$this->add('text', 'release_frequency', ts('Release Frequency'), CRM_Core_DAO::getAttribute('CRM_Campaign_DAO_Survey', 'release_frequency'));
// release frequency
$this->add('text', 'release_frequency', ts('Release Frequency'), CRM_Core_DAO::getAttribute('CRM_Campaign_DAO_Survey', 'release_frequency'));