phorge-phorge/src/applications/settings/setting/PhabricatorSelectSetting.php

<?php

abstract class PhabricatorSelectSetting
  extends PhabricatorSetting {

  abstract protected function getSelectOptions();

  final protected function newCustomEditField($object) {
    $setting_key = $this->getSettingKey();
    $default_value = $object->getDefaultValue($setting_key);

    $options = $this->getSelectOptions();

    if (isset($options[$default_value])) {
      $default_label = pht('Default (%s)', $options[$default_value]);
    } else {
      $default_label = pht('Default (Unknown, "%s")', $default_value);
    }

    $options = array(
      '' => $default_label,
    ) + $options;

    return $this->newEditField($object, new PhabricatorSelectEditField())
      ->setOptions($options);
  }

  final public function validateTransactionValue($value) {
    if (!strlen($value)) {
      return;
    }

    $options = $this->getSelectOptions();

    if (!isset($options[$value])) {
      throw new Exception(
        pht(
          'Value "%s" is not valid for setting "%s": valid values are %s.',
          $value,
          $this->getSettingName(),
          implode(', ', array_keys($options))));
    }

    return;
  }

  public function getTransactionNewValue($value) {
    if (!strlen($value)) {
      return null;
    }

    return (string)$value;
  }

}