I am trying to put this code in a more flexible manner so it can work whatever the size of $sets array is. I suppose it can be done with recursion but cannot find the correct php syntax.
$sets = array(
array(0, 1, 2, 3),
array(0, 1, 2, 3),
array(0, 1, 2, 3),
array(0, 1, 2, 3)
);
$combinations = array();
foreach($sets[0] as $s1)
foreach($sets[1] as $s2)
foreach($sets[2] as $s3)
foreach($sets[3] as $s4)
$combinations[] = array($s1, $s2, $s3, $s4);
print_r($combinations);