Yii - 如何向控制器中可以访问的表单添加自定义字段？

I have a Yii form based off a database model/table that I now want to add a custom field too that can then be accessed in the corresponding controller.

So the custom field DOES NOT correspond to a column in the database table.

Can this be done? If so how?

My motivation for doing this is to add a form value that I check, and I only process the form IFF that form value is empty. The field is hidden using CSS, so humans won't see it, and will hopefully be a simple convenient way to minimize spam. Since a bot is likely to fill out the form indiscriminately.
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Hope this makes sense.

Thanks!

Between start & end of rendering your form insert hidden (for example) next:

<?php echo CHtml::hiddenField('hidden_secret',''); ?>

Than in controller:

$hidden_secret = Yii::app()->request->getParam('hidden_secret'));

You need to add simple property to model:

class User extends CActiveRecord {
    public $myField;
}

Also do not forget to add its field in rules() if so required