$results = array(1, 2, 3, 4, 5, 6);
echo "<li>";
foreach($results as $pos => $result) {
if ($pos > 2 && $pos % 2 == 0) {
echo "</li>\n<li>";
}
echo "<div>result $result</div>";
}
echo "</li>";
или более просто:
$results = array(1, 2, 3, 4, 5, 6);
$max = count($results);
for($i = 0; $i < $max; $i++) {
echo "<li>";
echo "<div>result " . $results[$i] . "</div>";
$i++;
echo "<div>result " . $results[$i] . "</div>";
echo "</li>";
}