gistfile1.php

<?php

class BaseDoctrineForm extends sfFormDoctrine
{
  // ...

  protected function getRequiredFields(sfValidatorSchema $validatorSchema = null,
                                       $format = null)
  {
    if (is_null($validatorSchema))
    {
      $validatorSchema = $this->validatorSchema;
    }

    if (is_null($format))
    {
      $format = $this->widgetSchema->getNameFormat();
    }

    $fields = array();

    foreach ($validatorSchema->getFields() as $name => $validator)
    {
      $field = sprintf($format, $name);
      if ($validator instanceof sfValidatorSchema)
      {
        // recur
        $fields = array_merge(
          $fields,
          $this->getRequiredFields($validator, $field.'[%s]')
        );
      }
      else if ($validator->getOption('required'))
      {
        // this field is required
        $fields[] = $field;
      }
    }

    return $fields;
  }
}