count checked checkboxes

[BEFOR]

I need to check the # number of checkboxes that have actually been checked on a page (so to insert the value into a table).

checkboxes appear as:

<input type="checkbox" name="commercial[]"

<?php $checkbox= 'commercial[]';
$howmany=count($checkbox);
for ($x=0;$x<$howmany;$x++)
{
echo $howmany[$x]; }; ?>

Something's not quite right here - but how can this be made to count the checked checkboxes on an Update form ( that is, how can code "count" either while selections are made or by the "Submit")?

[kakki]

so you only need to count how many? .... thats

$howMany = sizeof ( $_REQUEST[ 'commercial' ] );

or do you want to do some code on checked checkboxes??
that could be done by giving individual names to the checkboxes
( "commercial_1", "commercial_2" .... ) and check that input
with:

for ( $i=1; $i<$HOW_MANY_CHECKBOXES; ++ $i )
{
       if ( isset ( $_REQUEST[ 'commercial_' . $i ] ) )
       {
               // your code here
       }
}