<?php
  if (isset($_POST['select_band'])) {
    $selected_band_id = $_POST['select_band'];
  }
?>

<form method="post" name="form_band" action="">
  <select name="select_band" onchange="javascript: submit()">
    <?php
      while ($row = mysqli_fetch_assoc($result)) {
        echo "<option value=".$row["band_id"] . ">" .$row["title"] ."</option>";
      }
    ?>
 </select>
</form>