PHP, MYSQL checking if a user is owner of a page - php

Question

I am trying to check if a user is the owner of a profile page so that i can display a text box for entering twitter similar posts.
The code
$id=mysql_query("SELECT id FROM users WHERE`username`='".$_GET['username']."'");
$ultimatum_form ='';
if(isset($_SESSION['id'])){
if($_SESSION['id']==$id){
$ultimatum_form = 'Write an ultimatum!(220 char max)<br/>
<form action="profile.php" method="post" enctype="multipart/form-data" name="ultimatum_form">
<textarea name="ultimatum_field" rows="3" style="width:97%;"></textarea>
</form>';
}
}
print "$ultimatum_form";
in my DB i have a table called "users", the table users has the columns "firs", "last", "username", "password", "email" and "id".
If i set $ultimatum_form outside of the session check it outputs the text-field and it works. The problem is that if i then go to another persons profile i can see the text-field and write posts for them.

Answer 1

You need to get data from the query:
$id=mysql_query("SELECT id FROM users WHERE`username`='".$_GET['username']."'");
$r = mysql_fetch_assoc($id);
$id = $r['id'];
then $id contains the row "id" value.
look into pdo/mysqli, mysql won't wrok in next php version.
here, better:
$id=mysql_query("SELECT id FROM users WHERE`username`='".$_GET['username']."'");
$r = mysql_fetch_assoc($id);
$id = $r['id'];
if(isset($_SESSION['id']))
{
if($_SESSION['id']==$id)
{
echo '
Write an ultimatum!(220 char max)<br/>
<form action="profile.php" method="post" enctype="multipart/form-data" name="ultimatum_form">
<textarea name="ultimatum_field" rows="3" style="width:97%;"></textarea>
</form>';
}
else
{
// Not users profile page
}
}

Answer 2

You can't exactly do what you're doing. You need to fetch the records.
$results = mysql_fetch_array(mysql_query("SELECT id FROM users WHERE`username`='".$_GET['username']."'"));
Then you can do:
if($_SESSION['id']==$results['id']){