Formularios: Combos múltiples

<?php
if (isset($_POST["cineastas"])) {
print_r($_POST["cineastas"]);
}
?>
<form action="multiple.php" method="post">
<select name="cineastas[]" multiple="multiple">
  <option value="1">aaa</option>
  <option value="2">bbb</option>
  <option value="3">ccc</option>
  <option value="4">ddd</option>
  <option value="5">eee</option>
</select>
<input type="submit" value="Enviar">
</form>