<div class="form-group">
                                                    <label>Hora de inicío</label>';

                                                                // Make a DateTime object with the current date and time
                                                                $today = new DateTime();

                                                                // Make an empty array to contain the hours
                                                                $aHours = array();

                                                                // Make another DateTime object with the current date and time
                                                                $oStart = new DateTime('now');

                                                                // Set current time to midnight
                                                                $oStart->setTime(0, 0);

                                                                // Clone DateTime object (This is like 'copying' it)
                                                                $oEnd = clone $oStart;

                                                                // Add 1 day (24 hours)
                                                                $oEnd->add(new DateInterval("P1D"));

                                                                // Add each hour to an array
                                                                while ($oStart->getTimestamp() < $oEnd->getTimestamp()) {
                                                                    $aHours[] = $oStart->format('H');
                                                                    $oStart->add(new DateInterval("PT1H"));
                                                                }

                                                                // Create an array with halfs
                                                                $halfs = array(
                                                                    '0',
                                                                    '30',
                                                                );

                                                                // Get the current quarter
                                                                $currentHalf = $today->format('i') - ($today->format('i') % 30);
                                                                ?><div class="form-group">
                                                                <select name="vaivaivai" id="">
                                                                    <option value="-1">Choose a time</option>
                                                                    <option value="$hora_inicio" selected><?= $hora_inicio ?></option>
                                                                    <?php foreach ($aHours as $hour): ?>
                                                                        <?php foreach ($halfs as $half): ?>
                                                                            <option value="<?= sprintf("%02d:%02d", $hour, $half); ?>" <?= ($hour == $today->format('H') && $half == $currentHalf) ? : ''; ?>>
                                                                                <?= sprintf("%02d:%02d", $hour, $half); ?>
                                                                            </option>
                                                                        <?php endforeach; ?>
                                                                    <?php endforeach; ?>
                                                                </select></div><?php

                                                                if (isset($_SESSION["hora"])) {
                                                                    if ($_SESSION["hora"] == 1) {
                                                                        echo "<div class='alert alert-danger'>
                <strong>Erro!</strong> Hora inválida!
          </div>";
                                                                        $_SESSION["hora"] = 0;
                                                                    }
                                                                }

                                                                echo '<div class="form-group">
                                                    <label>Duração</label>
                                                    <input class="form-control" name="duracao" value="' . $duracao . '">
                                                </div>';