How to use CakePHP's built-in validation helpers?

@arnoldo.moen 

CakePHP provides several built-in validation helpers that allow you to easily validate data in your application. Here's an example of how to use these helpers:

1. Start by creating a validation rule in your model. For example, if you have a User model with an email field, you can add a validation rule like this:

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// in User.php
public $validate = array(
    'email' => array(
        'rule' => 'email',
        'required' => true,
        'message' => 'Please enter a valid email address'
    )
);

This rule checks that the email field is a valid email address and is required.

1. In your controller, you can then use the validate method to validate the data. For example, if you're processing a form submission, you might do something like this:

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// in UsersController.php
public function add() {
    if ($this->request->is('post')) {
        $this->User->set($this->request->data);
        if ($this->User->validates()) {
            // save the user
        }
    }
}

Here, we're setting the data to be validated with set, and then calling validates to check that it meets the validation rules.

1. If the data doesn't pass validation, you can retrieve the validation errors using the validationErrors property of the model:

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$errors = $this->User->validationErrors;

You can then use these errors to display feedback to the user about what went wrong.

There are many other validation helpers available in CakePHP, such as notEmpty, numeric, date, and more. You can find more information on these helpers in the official CakePHP documentation.