BaseDoctrineForm.class.php

<?php

class BaseDoctrineForm extends sfFormDoctrine
{
  public function __construct($object = null, $options = array(), $CSRFSecret = null)
  {
    parent::__construct($object, $options, $CSRFSecret);

    // tell the widget schema which fields are required
    $this->widgetSchema->addOption('required_fields', $this->getRequiredFields());

    $this->widgetSchema->addFormFormatter('table', new RequiredLabelsFormatterTable($this->widgetSchema));
  }

  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;
  }
}

RequiredLabelsFormatterTable.class.php

<?php

class RequiredLabelsFormatterTable extends sfWidgetFormSchemaFormatterTable
{
  protected
    $requiredLabelClass = 'required';

  public function generateLabel($name, $attributes = array())
  {
    // loop up to find the "required_fields" option
    $widget = $this->widgetSchema;
    do
    {
      $requiredFields = (array) $widget->getOption('required_fields');
    }
    while ($widget = $widget->getParent());

    // add a class (non-destructively) if the field is required
    if (in_array($this->widgetSchema->generateName($name), $requiredFields))
    {
      $attributes['class'] = isset($attributes['class']) ?
        $attributes['class'].' '.$this->requiredLabelClass :
        $this->requiredLabelClass;
    }

    return parent::generateName($name, $attributes);
  }
}