$i++ * 100, how to?

I have this code:

<?
$i=0;

if (isset($_GET['x'])) { 
echo "x ".$i++;
}

if (isset($_GET['y'])) { 
echo "y ".$i++;
}

if (isset($_GET['z'])) { 
echo "z ".$i++;
}

if (isset($_GET['w'])) { 
echo "w ".$i++;
}

?>

Code (markup):

Now, what I need to do is that starting from zero (the first one) I have to increase each GET (if set) with 100.

Like this:
if is set get 1 my $i should be 0,
if is set get 2 my $i should be 100,
if is set get 3 my $i should be 200,
if is set get 4 my $i should be 300.

How can I do that? I have tried to start with a $i=0*100; but that is not working.

 

$i = 0*100 is equal to zero, therefore its not working.

Maybe this

$i=0;

if (isset($_GET['x'])) { 
echo "x ".$i;
$i+=100;
}

if (isset($_GET['y'])) { 
echo "y ".$i;
$i+=100;
}

if (isset($_GET['z'])) { 
echo "z ".$i;
$i+=100;
}

if (isset($_GET['w'])) { 
echo "w ".$i;
$i+=100;
}

PHP:

or the simplified version:

$getarray = array('x','y','z','w');
$i=0;
foreach ($getarray as $get) {
if (isset($_GET[$get])) {
echo $get.' '.$i;
$i+=100;
}
}

PHP:

 

Thanks! I managed to do it with

echo "w ".$i++*100;