Workhours selection.php

<?php 

echo "<select>";
$hora = strtotime('00:00');
$i = 0;
$tempo = ceil($hora / (15*60)) * (15*60);
while($i < 96) {
    echo '<option value="'. date('H:i', $tempo) .'">' . date('H:i', $tempo) . '</option>'."\n";
    $tempo = strtotime('+15 minutes', $tempo);
    $i++;
}
echo "<option value='23:59'>23:59</option>";
echo "</select>";

?>