Writing your own validators

Yii provides a good set of built-in form validators that cover the most typical developer needs and are highly configurable. However, in some cases, a developer may need to create a custom validator.

This recipe is a good example of creating a standalone validator that checks the number of words.

Getting ready

Create a new application by using the Composer package manager, as described in the official guide at http://www.yiiframework.com/doc-2.0/guide-start-installation.html.

How to do it...

1. Create a standalone validator at @app/components/WordsValidator.php as follows:

   <?php
   namespace app\components;
   use yii\validators\Validator;
   class WordsValidator extends Validator
   {
       public $size = 50;
       public function validateValue($value){
           if (str_word_count($value) > $this->size) {
               return ['The number of words must be less than {size}', ['size' => $this->size]];
           }
           return false;
       }
   }

2. Create an Article...