delete value from database using link

I have a page that shows comments, "comments.php", and I include the page on any other page that I want comments to show. I am trying to implement a way to delete comments if needed. Each comment has an auto-increment "commentID". Right now I'm using an action, and then just using a link to call the action.

When I hover over the link, the URL looks correct, but when I click it, the page refreshes and nothing happens. Any ideas?

Action:

if ($_POST['action'] == 'delete') {
    $sql = "delete from " . $db_prefix . "comments where commentID = " . (int)$_GET['id'];
    mysql_query($sql) or die('error deleting user: ' . $sql);
header('Location: ' . $_SERVER['HTTP_REFERER']);
}

Show comments and show link to delete: (unnecessary code has been left out)

echo '<a href="/comments.php?action=delete&id=' . $result['commentID'] . '">delete</a> 

What am I doing wrong?

via Chebli Mohamed