wrong code in cookbook?

I try to test http://www.yiiframework.com/doc/cookbook/24/

Creating a dependent dropdown

if i type this in veiw-file like in cookbook

echo CHtml::dropDownList('country_id', '', array(1=>'USA',2=>'contry 2',2=>'contry 3'),

but $_POST’country_id’ is empty and second droplist is not changed.

if i change code in controller:


array(':parent_id'=>(int) '1'));

everything work - second droplist ok. What is wrong with $_POST’country_id’? Can anyone help me?