Form-level errors with Zend_Form

May 10, 2008 10:21:42 AM

Tags: PHP Zend Framework

One feature that I believe is lacking from an out-of-the-box Zend_Form setup is form-level errors. Form-level errors are not tied to one particular element; instead, they apply to the form as a whole. Examples might include 'Invalid login credentials' (which applies to entire login form), or 'There was an error processing your form' (if a database query fails). These types of error messages are not catered for.

There are a number of ways to achieve form-level errors. The easiest is to stick the error message in the view as $formError and just render it above $form->render() if it is set. I like this solution because it doesn't require any subclassing, but I'd prefer to have a solution which renders form-level errors as part of $form->render().

<?php

// controller

$form = new Zend_Form(...);

$this->view->form = $form;

if ($this->getRequest()->isPost())
{
	if ($form->isValid($_POST))
	{
		try
		{
			// ...
		}
		catch (Exception $e)
		{
			$this->view->formError = '....';
		}
	}
}

// view

if ($this->formError !== NULL)
{
	echo $this->formError;
}

echo $this->form->render();

Nice and simple, but doesn't really encapsulate all form handling within Zend_Form. Furthermore, using this technique couples the controller and view more strongly, and I'd say that goes somewhat against the Zend Framework methodology.

So an alternative, and the mechanism I'm using now, is to subclass Zend_Form. Cosider App_Form below:

<?php

class App_Form extends Zend_Form
{
	protected $_formError = NULL;

	function __construct ($options = NULL)
	{
		$this->setDisableLoadDefaultDecorators(true);		
		$this->addPrefixPath('App_Form', 'App/Form/');
		parent::__construct($options);
		$this	->addDecorator('FormElements')
			->addDecorator('HtmlTag', array('tag' => 'dl', 'class' => 'zend_form'))
			->addDecorator('FormError')
			->addDecorator('Form');
	}

	public function setFormError ($error)
	{
		if (is_array($error))
		{
			$this->_formError = $error;
		}
		else if (is_string($error))
		{
			$this->_formError = array($error);
		}
		else
		{
			throw new Zend_Exception('$error must be a string or an array');
		}
	}

	public function addFormError ($error)
	{
		if (! is_string($error))
		{
			throw new Zend_Exception('$error must be a string');
		}
		if (is_array($this->_formError))
		{
			$this->_formError[] = $error;
		}
		else
		{
			$this->_formError = array($error);
		}
	}

	public function getFormError ()
	{
		return $this->_formError;
	}

	public function isFormError ()
	{
		return $this->_formError !== NULL;
	}
}

The constructor above creates a standard form, with the addition of the FormError decorator, shown below. The other functions in App_Form write and read the form-level errors.

<?php

class App_Form_Decorator_FormError extends Zend_Form_Decorator_Abstract
{
	public function render ($content)
	{
		$form = $this->getElement();
		
		$errorContent = '';
		
		if ($form instanceof App_Form)
		{
			if ($form->isFormError())
			{
				$errorContent = '<ul><li>';
				$errorContent .= join('</li><li>', $form->getFormError);
				$errorContent .= '</li></ul>';
			}
		}
		
		return $errorContent.$content;
	}
}

My FormError decorator just shows a list of errors above the DL that contains the form elements. A nice thing to note is that the order in which decorators are added to the form is important: if you switch the addition of the Form and FormError decorators in App_Form's constructor, the list of errors will appear above the <form> tag.

Putting it all together:

<?php

// controller

$form = new App_Form(...);

$this->view->form = $form;

if ($this->getRequest()->isPost())
{
	if ($form->isValid($_POST))
	{
		try
		{
			// ...
		}
		catch (Exception $e)
		{
			$form->addFormError('...');
		}
	}
}

// view

echo $this->form->render();

Any other suggestions?

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