php使用check box

if (isset($_POST['submit'])) {
    foreach ($_POST['todelete'] as $delete_id) { //这里是循环遍历这个数组 todelete 每一个值被设置成 $delete_id
      $query = "DELETE FROM email_list WHERE id = $delete_id";
      mysqli_query($dbc, $query)
        or die('Error querying database.');
    } 

    echo 'Customer(s) removed.<br />';
  }

  // Display the customer rows with checkboxes for deleting
  $query = "SELECT * FROM email_list";
  $result = mysqli_query($dbc, $query);
  while ($row = mysqli_fetch_array($result)) {

    // todelete[]是一个数组 能够把checkbox中选中的放到这个数组中
    echo '<input type="checkbox" value="' . $row['id'] . '" name="todelete[]" />'; 
    echo $row['first_name'];
    echo ' ' . $row['last_name'];
    echo ' ' . $row['email'];
    echo '<br />';
  }