Question

I assume that :parent_id evaluates to a number. But, how exactly does this piece of code work? When should I use this syntax (:name)?

$data = Location::model()->findAll('parent_id=:parent_id',array(
                ':parent_id' => (int) $_POST['Current-Controller']['country_id']
        ));

Answer 1

The colon doesn’t have any special meaning. The pattern :parent_id as a whole does, but that’s only because you chose to use it as a variable name in the WHERE condition (parent_id=:parent_id).

You could just as well have chosen to write

$data=Location::model()->findAll('parent_id=the_quick_brown_fox',
     array('the_quick_brown_fox'=>(int) $_POST['Current-Controller']['country_id']));

In practice the colon is used because there’s the risk of the name you choose for the variable also being present as a legitimate part of the condition, in which case all instances of it will be replaced with the value and results will be unexpected.

For example, this:

$data=Location::model()->findAll('parent_id=parent_id',
     array('parent_id'=> 1 /*anything, really*/));

would result in the condition 1=1, which would match all records.