Web Technology: A Revolution

On its 1.1 release, CakePHP only allowed us to define one rule of validation per field. If we needed to specify more than one rule, we either had to use some handy extensions to CakePHP that are available, or achieve multiple validation by using the callback method beforeValidate() in our models. CakePHP 1.2 brings us an improved technique to specify multiple rules per field, and best of all, it’s backwards compatible, so our existing rules will continue to work.

What better way to start that with an example, specifically the typical Article CRUD example. We start by creating a simple controller that provide us with an add form:

Controller Class:

Download code <?php
class ArticlesController extends AppController {
var $name = ‘Articles’;
var $helpers = array(‘Form’);

function add() {
if (!empty($this->data)) {
// We don’t do any real saving, we just validate the model

if ($this->Article->create($this->data) && $this->Article->validates()) {
$this->set(‘valid’, true);
}
}
}
}
?>

and its matching articles/add.ctp view:

View Template:

Download code
<?php echo $form->create(‘Article’); ?>
<?php echo $form->input(‘title’); ?>
<?php echo $form->input(‘body’); ?>
<?php echo $form->end(‘Add Article’); ?>


Let’s take the classic Article model, and add only one validation to some fields:

Model Class:

Download code <?php
class Article extends AppModel {
var $name = ‘Article’;
var $validate = array(
‘title’ => VALID_NOT_EMPTY,
‘body’ => VALID_NOT_EMPTY
);
}
?>

Nothing new here, except that as you can see we’re not defining the error messages. We are going to do so in the view. So we go back and change the add.ctp view so it now looks like this:

View Template:

Download code
<?php echo $form->create(‘Article’); ?>
<?php echo $form->input(‘title’, array(‘error’ => ‘Please specify a valid title’)); ?>
<?php echo $form->input(‘body’, array(‘error’ => ‘Please specify a valid body’)); ?>
<?php echo $form->end(‘Add Article’); ?>


If we try the add action and submit the form with both fields empty, we’ll get our newly defined error messages. What if we also wanted to add another rule of validation for the title field, where we should check that the title is at the most 100 characters long? Let’s review the model, and now change it to look like this:

Model Class:

Download code <?php
class Article extends AppModel {
var $name = ‘Article’;
var $validate = array(
‘title’ => array(
VALID_NOT_EMPTY,
array(
‘rule’ => array(‘maxLength’, 100)
)
),
‘body’ => VALID_NOT_EMPTY
);
}
?>

We have just converted the ‘title’ field to consist of an array of rules. The first rule is a CakePHP provided regular expression that checks for a specified value, and the second rule is a method existing in CakePHP’s built in Validation class called ‘maxLength’. Since this method takes an extra parameter (the number of maximum characters the field can contain), we add it on an array.

So we have now two conditions that can generate an error for the field title: an empty value, or a value with more than 100 characters. How do we differentiate the error messages on the view? Let’s change the view so it now looks like:

View Template:

Download code
<?php echo $form->create(‘Article’); ?>
<?php echo $form->input(‘title’, array(‘error’ => array(
0 => ‘Please specify a valid title’,
1 => ‘The title must have no more than 100 characters’
))); ?>
<?php echo $form->input(‘body’, array(‘error’ => ‘Please specify a valid body’)); ?>
<?php echo $form->end(‘Add Article’); ?>


As you can see we’re setting an error message per rule. 0 corresponds to the first rule, 1 to the second, and so on. If we wanted more flexibility (such as having the option to change the order of the rules and still have the same error message assignment) and needed more readability, we can then use the string index approach. Change the model so it now looks like:

Model Class:

Download code <?php
class Article extends AppModel {
var $name = ‘Article’;
var $validate = array(
‘title’ => array(
‘required’ => VALID_NOT_EMPTY,
‘length’ => array( ‘rule’ => array(‘maxLength’, 100) )
),
‘body’ => VALID_NOT_EMPTY
);
}
?>

and change the view so it now looks like:

View Template:

Download code
<?php echo $form->create(‘Article’); ?>
<?php echo $form->input(‘title’, array(‘error’ => array(
‘required’ => ‘Please specify a valid title’,
‘length’ => ‘The title must have no more than 100 characters’
))); ?>
<?php echo $form->input(‘body’, array(‘error’ => ‘Please specify a valid body’)); ?>
<?php echo $form->end(‘Add Article’); ?>


Custom Validation

What about custom validation? What if we needed more rules than those provided by CakePHP’s Validation class? Don’t sweat, it comes very easy! All you need to do is set up your own validation functions on either your model or your AppModel class (if you wish to share them across your models.) For example, we’re going to add a new validation rule to allow us to specify a minimum and a maximum length for our title. I know, what’s the point when we have both minLength and maxLength in CakePHP’s Validation class? Well, to show how it can be done

Edit the model and change it so it now looks like this:

Model Class:

Download code <?php
class Article extends AppModel {
var $name = ‘Article’;
var $validate = array(
‘title’ => array(
‘required’ => VALID_NOT_EMPTY,
‘length’ => array( ‘rule’ => ‘validateLength’, ‘min’ => 5, ‘max’ => 100 )
),
‘body’ => VALID_NOT_EMPTY
);

function validateLength($value, $params = array()) {
$valid = false;

$params = am(array(
‘min’ => null,
‘max’ => null,
), $params);

if (empty($params['min']) || empty($params['max'])) {
$valid = false;
} else if (strlen($value) >= $params['min'] && strlen($value) <= $params['max']) {
$valid = true;
}

return $valid;
}
}
?>

A custom validation function takes one mandatory first parameter: the value to validate, and must return a boolean value of true when the value validates, or false when it doesn’t. Extra parameters will be sent to the validation function as an array through its second parameter, and the values in the array are those values specified in the validation rule that do not correspond to CakePHP’s internal values (such as rule or allowEmpty.)