Yii validation  Form in Model
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Go to your  model file and find function

 public function rules() {
        return array(
        array('firstname, lastname, email, username,password,address1,phone, mobile,is_active','required'),
        array('firstname, lastname, email, username, password, address1, address2', 'length', 'max'=>255),
        array('email','email'),
        array('phone, mobile', 'length', 'max'=>11),
        array('mobile', 'numerical', 'integerOnly'=>true),
        array('phone', 'numerical', 'integerOnly'=>true),
        array('is_active', 'length', 'max'=>8),
        array('created_at, updated_at', 'default', 'setOnEmpty' => true, 'value' => null),
        array('r_password', 'compare','compareAttribute'=>'password',),
        array('id, firstname, lastname, email, username, password, address1, address2, phone, mobile, extra, is_active', 'safe', 'on'=>'search'),
        );
    }