CakeForm, an easy way to define custom cakephp forms

cake_form.php

<?php

class CakeForm {

    var $_boundValues   = array();
    var $_errors        = null;
    var $_formHelper    = null;

    var $_execute       = null;
    var $_format        = 'ul';
    var $_fields        = array();

/**
 * Labels for all fields
 *
 * Fields to not need to be set here in order to have labels
 * If a field is not set, label defaults to Inflected version
 * of the fieldName
 *
 * If set to null, then no label is created
 *
 * @var array
 * @todo implement
 */
    var $_labels        = array();

/**
 * Rules to implement for each field
 *
 * Rules are implemented exactly as model validation
 * rules are implemented
 *
 * @var array
 * @todo implement
 */
    var $_rules         = array();

    function bindValues() {
        
    }

    function errors() {}

    function isValid() {}

/**
 * Executes an internally 
 *
 * @return void
 * @author Jose Diaz-Gonzalez
 */
    function execute() {
        if (!empty($this->_execute)) {
            return $this->{$this->_execute}($this->_boundValues);
        }
    }

/**
 * Constructs the inner portion of a form, sans create/input
 *
 * @return void
 * @author Jose Diaz-Gonzalez
 */
    function __toString() {
        $output = array();

        foreach ($this->_fields as $field => $type) {
            $input = $this->_input($field, $type);

            if ($this->_format === 'table') {
                $output[] = "<tr><td>{$input}</td></tr>";
            } else if (in_array($this->_format, array('ol', 'ul'))) {
                $output[] = "<li>{$input}</li>";
            } else if ($this->_format === 'span') {
                $output[] = "<span>{$input}</span>";
            }
        }

        if ($this->_format === 'table') {
            array_unshift($ouput, '<table><tbody>');
            $output[] = '</table></tbody>';
        } else if (in_array($this->_format, array('ol', 'ul'))) {
            array_unshift($ouput, '<ol>');
            $output[] = '</ol>';
        } else if ($this->_format === 'span') {
            array_unshift($ouput, '<ul>');
            $output[] = '</ul>';
        }

        return implode($output);
    }

    function _input($fieldName, $options = array()) {
        if (is_string($options)) $options = array('type' => $options);

        if (!$this->_formHelper) {
            App::import('Helper', 'Form');
            $this->_formHelper = new FormHelper;
        }

        switch ($options['type']) {
            case 'hidden':
                $input = $this->_formHelper->hidden($fieldName, $options);
                $format = array('input');
            break;
            case 'checkbox':
                $input = $this->_formHelper->checkbox($fieldName, $options);
            break;
            case 'radio':
                $radioOptions = (isset($options['options'])) ? (array) $options['options'] : array();
                $input = $this->_formHelper->radio($fieldName, $radioOptions, $options);
            break;
            case 'text':
            case 'password':
            case 'file':
                $input = $this->_formHelper->{$type}($fieldName, $options);
            break;
            case 'select':
                $options += array('options' => array());
                $list = $options['options'];
                unset($options['options']);
                $selected = (isset($options['selected'])) ? $options['selected'] : null;
                $input = $this->_formHelper->select($fieldName, $list, $selected, $options);
            break;
            case 'textarea':
            default:
                $input = $this->_formHelper->textarea($fieldName, $options + array('cols' => '30', 'rows' => '6'));
            break;
        }

        return $input;
    }

}

login_form.php

<?php

class LoginForm extends CakeForm {
    var $_name      = 'Form';
    var $_execute   = 'authenticate'; // Defaults to null, or a function in this class
    var $_format    = 'ul';        // [table, ol, ul, span, none]
    var $_fields = array(
        'username' => 'text',
        'password' => 'password',
    );
    var $_labels = array(
        'username' => 'Email or Username',
        'password' => 'Password'
    );
    var $_rules = array(
        'username' => array(
            'notempty' => array(
                'message' => 'Cannot be left empty'),
            'minlength' => array(
                'length' => 4,
                'message' => 'Must be at least 4 characters'
            ),
            'string' => array(
                'message' => 'Invalid input'
            ),
        ),
        'password' => array(
            'string' => array(
                'message' => 'Invalid input'
            ),
        )
    );

    function authenticate($params) {
        $User = ClassRegistry::init('User');

        return $User->authenticate($params['username'], $params['password']);
    }

}