Flourish フレームワークでフォーム処理を使用するにはどうすればよいですか?

<?php
$form = new lourishForm(array(
    'method' => 'post',
    'action' => '/submit',
));
$form->append('text', 'name', 'Your name', array(
    'required' => true,
));
$form->append('email', 'email', 'Your email', array(
    'required' => true,
));
$form->append('textarea', 'message', 'Your message', array(
    'required' => true,
));
echo $form;

<?php
$form = new lourishForm(array(
    'method' => 'post',
    'action' => '/submit',
));
$form->append('text', 'name', 'Your name', array(
    'required' => true,
));
$form->append('email', 'email', 'Your email', array(
    'required' => true,
));
$form->append('textarea', 'message', 'Your message', array(
    'required' => true,
));

if ($form->handle_submission()) {
    echo 'Your message was sent.';
} else {
    echo $form;
}

<?php
class Custom_Field extends lourishForm_Field
{
    public function __construct($name, $label = '', $options = array())
    {
        parent::__construct($name, $label, $options);
    }
    public function set_value($value)
    {
        $this->value = $value;
    }

    public function to_html()
    {
        return '<input type="hidden" name="' . $this->name . '" value="' . $this->value . '">';
    }
}

$form = new lourishForm(array(
    'method' => 'post',
    'action' => '/submit',
));
$form->append(new Custom_Field('custom', 'Custom field', array(
    'value' => 'custom_value',
)));

echo $form;