Delete something from sql - php

Question

I want to delete columns in my sql, which is going with succes. But there is another problem, I need to solve. I've tried and checked here around. All with any kind of succes I will try to explain my problem.
I've a member system where you can add your content, edit you submitted content and now I'm creating to delete your content. My script can delete now post which are created by the same user as logged in. For example my account is called Bobby and someone is called Alex I cannot delete the content of Alex only mimes, thats what I want.
For example my content link of bobby : category.php?nameID=cat2&id=22 And the delete link is deletepost.php?id=22
EX. content link Alex:
category.php?nameID=cat2&id=23 And the delete link is deletepost.php?id=23
When I'm logged in as Bobby and I go to deletepost.php?id=23 and receive a message like You cannot delete this content!
And When I go to mimes deletepost.php?id=22 I need to receive a message like: Your content has been delete succesfully!
I'm only receive NO!
<?php
$user = new User();
if (isset($_GET['id'])) {
$id = mysql_real_escape_string($_GET['id']);
if(!$user->isLoggedIn()) {
Redirect::to('index.php');
}
if($user->isLoggedIn()) {
$pakuser = $user->data()->username;
$sql = mysql_query("DELETE FROM post
WHERE post.id = '$id' AND post.add = '$pakuser'")
or die(mysql_error());
if (!$sql) {
echo 'NO';
}
if ($sql) {
echo 'YES';
}
}
}
?>

Answer 1

Beside from the possible sql injections in your code, you can try this format for a delete query to determine the mistake:
<?php
$sql = "
DELETE FROM
post
WHERE
post.id = ".$id." AND post.add = '".$pakuser."'
";
if(!$res = mysql_query($sql))
{
trigger_error(mysql_error().'<br />In query: '.$sql);
}
elseif(mysql_affected_rows() == 0)
{
echo 'No records Deleted. <br />Query: '.$sql;
}
else
{
echo 'There are '.mysql_affected_rows().' records deleted.';
}
?>
Are you also sure that post.add is the username?