<th>
                            Hora Inicio
                        </th>
                        <th>
                            Hora fin
                        </th>
                    </tr>
                </thead>
                <tbody>
                    <form  method="POST" action="index.php">
                        <input type="hidden" name="task" value="insertar-horario"/>  
                        <tr>
                            <td>
                                <select name='idAula'>
                                        <?php 
$listaAulas = $aulasBLL->selectAll();
foreach ($listaAulas as $objAula) {
    ?>
                                    <option value ="<?php 
    echo $objAula->getId();
    ?>
"> 
                                                <?php 
    echo $objAula->getNumero();
    ?>
                                            </option>
                                            <?php 
}
?>

                                </select>