I have used for loop to create checkboxes.
and on each of them i want to know its checked or unchecked.
code is as below:

foreach ($All_skill_type as $All_skill_type_)
                        $each_skill_type=$All_skill_type_ -> skill_type ;
                        // find skill_type_id and serach Skills for that skill_type
                        <fieldset class="step">
                                <label style='width:170px!important;'><? echo $each_skill_type .":";?></label>
                                    for ($i=0;$i<sizeof($skills_of_skill_type);$i++)
                                        echo CHtml::CheckBox($skill_box,'', array (
                                        echo CHtml::label($skill_box, $skill_box);

Above code is written in Yii framwork.

Now onclick of each checkbox, an calling function skill_check(),
but how to recognize whether the checkbox is checked or unchecked?