Grouping items in a foreach loop

For each Group 1

<?php
$i = 0;
$group = 0;
$group_by = 5;
while ($i < 19){
    $i++;
    if ($group == 0) {//new group start
        echo "<li>";
    }
    echo "<div>item " . $i . "</div>"; 
    $group++;
    if ($group == $group_by) {//end of group
       echo "</li>\n";
       $group = 0;
       $group_by = 6;
    }
}
if ($group != 0) { echo "</li>"; }

Output:

item 1

item 2

item 3

item 4

item 5

item 6

item 7

item 8

item 9

item 10

item 11

item 12

item 13

item 14

item 15

item 16

item 17

item 18

item 19