<?php

// form to embed symfony autogenerated forms

class swThreadForm extends sfFormSymfony {

    public function configure() {
        $this->embedForm('thread', new ThreadForm());
    }

}

// thread form - autogenerated

class ThreadForm extends BaseThreadForm {

    public function configure() {

        $this->useFields(array(
            'body',
        ));
}

// base thread form - autogenerated

abstract class BaseThreadForm extends BaseFormDoctrine {

    public function setup() {
        $this->setWidgets(array(
            'id' => new sfWidgetFormInputHidden(),
            'body' => new sfWidgetFormTextarea(),
        ));

        $this->setValidators(array(
            'body' => new sfValidatorString(array('max_length' => 10000)),
        ));

        $this->validatorSchema->setPostValidator(
                new sfValidatorDoctrineUnique(array('model' => 'Thread', 'column' => array('id')))
        );

        $this->errorSchema = new sfValidatorErrorSchema($this->validatorSchema);

        $this->setupInheritance();

        parent::setup();
    }

// the controller

    public function executeIndex(sfWebRequest $request) {
        $this->form = new swThreadForm();
    }

    public function executeCreate(sfWebRequest $request) {
        $this->form = new swThreadForm();

        if ($request->isMethod('post')) {
            $this->form->bind($request->getParameter('thread'));
            if ($this->form->isValid()) {
                $this->redirect('thread/welcome?' . http_build_query($this->form->getValues()));
            }
        }

        $this->setTemplate('index');
    }

// the index template

<form action="<?= url_for('thread/create') ?>" method="POST">

<?= $form['thread']['body']->renderLabel() ?>
<?= $form['thread']['body']->renderError() ?> // i always get REQUIRED no matter what i post
<?= $form['thread']['body']->render() ?>

<br /><br />

<input type="submit" value="Submit" />

</form>