Form with validation

A simple form with validation checks.

<pinp>
  $formFields = array(
    'Name',
    'Email' => array(
      'required'     => true,
      'checks'       => 'email'
    ),
    'Password' => array(
      'type'         => 'password',
      'required'     => true
    ),
    'agree' => array(
      'type'         => 'checkbox',
      'required'     => true,
      'checkedValue' => 1,
      'label'        => 'I agree to the terms of service.'
    )
  );

  $formButtons = array( 'Register', 'cancel' => 'Another time' );

  $form = ar('html')->form( $formFields, $formButtons );

  if ( $form->isSubmitted('button_0') ) 
  {
    if ( $form->isValid() ) 
    {
      echo 'Registration complete, thank you.';
    }
    else 
    {
      $invalidFields = $form->validate();
      $required = false;
      $errors = array();
      $formHTML = $form->getHTML();
      foreach ( $invalidFields as $name => $error ) 
      {
        $code = $error->getCode();
        switch ( $code ) 
        {
          case 'required' :
            if ( !$required ) 
            {
              $required = true;
              $errors[] = ar('html')->el( 'div', 
                'You must fill in the required fields.' );
            }
          break;

          default :
            $errors[] = ar('html')
              ->el( 'div', $error->getMessage() );
          break;					
        }
        $field = $formHTML->getElementById( $name );
        if ($field) 
        {
          $field->parentNode->setAttribute( 'class', 
            array( 'validation' => ' invalid' ) );
        }
      }
      if ( count($errors) ) 
      {
        echo ar('html')
          ->el( 'div', array( 'class' => 'formError'),
            ar('html')->nodes( $errors ) );
      }
      echo $formHTML;
    }
  } 
  else if ($form->isSubmitted('cancel')) 
  {
    echo 'Registration cancelled, see you later.';
  }
  else 
  {
    echo $form->getHTML();
  }
</pinp>