Whenever create a model using gii CRUID, it automatically generate for us all functions we need: edit, delete, create, read, also the form. Did you ever wonder how can it display the error message when we do a wrong form submit ? How could we customize that error message ?

The key is _form.php, we will see the code which help us display the error message.
<?php echo $form->error($model,'post_title'); ?>

The point is how can we customize the message display when it’s wrong with validation rule.

class Post extends CActiveRecord
{
    public function rules()
    {
        return array(
            array('post_title', 'required',
                  'message'=>'Please enter a value for {attribute}.'),
        );
    }
}

In this code above, line 7, there is a predefined placeholder {attribute}. The CRequiredValidator will replace the actual attribute name that fails the validation.