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Posted by Robert Cummings on 10/21/45 11:28
On Mon, 2005-10-03 at 14:11, John Taylor-Johnston wrote:
> Excellent. Thanks. I think I follow what you have done. But to
> clarify, and learn, what are you doing with -= ?
> $trolley[$item] -= $quantity;
> Likewise, i had not followed what you were doing with the lines I
> commented out. They did not seem to work, and I succeeded in doing
> what I wanted without them. I'm a prof, as you can tell, and always
> have a question for an answer ;).
> Thanks for your time and patience,
> John
> > if( isset( $trolley[$item] ) )
"isset" checks that the item with ID $item is in the trolley. No need to
decrease the quantity if it's not there.
> > {
> > $trolley[$item] -= $quantity;
The expression:
$trolley[$item] -= $quantity;
is a short form for the following:
$trolley[$item] = $trolley[$item] - $quantity;
Essentially we decrease the quantity of the given item by $quantity.
> > if( $trolley[$item] < 1 )
> > {
Above we check if we subtracted more items than is physically possible
:)
> > unset( $trolley[$item] );
If there are 0 or less items then there's no point having 0 of the item
in the trolley, so we unset the item from the array, which essentially
removes it completely. To view the difference at each step you can do
the following:
<?php
if( isset( $trolley[$item] ) )
{
echo "Trolley before removing $quantity of $item<br />";
trolleyPrint();
$trolley[$item] -= $quantity;
echo "Trolley after removing $quantity of $item<br />";
trolleyPrint();
if( $trolley[$item] < 1 )
{
unset( $trolley[$item] );
echo "Trolley after cleaning up empty entry for $item<br />";
trolleyPrint();
}
}
?>
Cheers,
Rob.
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