Update and insert category and moderator - php

Question

I have file category.php where i have:
Category name / Moderator
Economy / uername1
Math / username2
Biology / username1
Every category i can update and add new category with username who can moderate some category.
I have problem with categorie.php because when i click update on label Category name in input write me Economy and username1 when i click on update some other category like Math in input writes me again Economy and username1.
Second problem i have is when i want to add a new category with moderator. After i click submit doesn't insert in my mysql database name of added category with moderator.
<?PHP
session_start();
if(!isset($_SESSION["type_id"])){
header("Location:index.php");
exit();
}
else if($_SESSION["type_id"]!=0)
{
header("Location:index.php");
exit();
}
include_once("meni.php"); ?>
<div class="mid-right"><?php
$dbc=mysql_connect("localhost","2013","013");
if (!$dbc)
{
echo 'Error!'.mysql_error();
exit();}
$db=mysql_select_db("2013_db",$dbc);
$category = $category_id = $name = $user_id = "";
$id = 0;
if(isset($_POST['username'])) {
if (isset($_POST['type_id'])) {
$type_id = $_POST['type_id'];
} else {
$type_id = 2;
}
$id = $_POST['new'];
if ($id == 0) {
$name = $_POST['name'];
$user_id = $_POST['user_id'];
$category_id = $_POST['category_id'];
$sql = "INSERT INTO category (category_id, name, user_id) VALUES ($category_id, '$name', '$user_id');";
}
$result=mysql_query($sql);
mysql_close($db);
header("Location: category.php");
}
if(isset($_POST['category_id']) && isset($_POST['name']) && isset($_POST['moderator']) && $_SESSION['type_id'] == 0) {
$name = $_POST['name'];
$user_id = $_POST['moderator'];
$category_id = $_POST['category_id'];
$sql = "UPDATE category SET name = '$name', user_id = $user_id WHERE category_id = $category_id";
$result=mysql_query($sql);
mysql_close($db);
header("Location: category.php");
}
if(isset($_GET['categories'])) {
$kategorija_id = $_GET['categories'];
if ($id==2) {
$id = $_SESSION["category_id"];
}
$dbc=mysql_connect("localhost","2013","2013");
if (!$dbc)
{
echo 'Error!'.mysql_error();
exit();}
$db=mysql_select_db("2013_db",$dbc);
$sql = "SELECT k.category_id, k.name, ko.username FROM category k, user ko WHERE k.user_id = ko.user_id AND ko.type_id = 1";
$result=mysql_query($sql);
list($category_id, $name, $user_id) = mysql_fetch_array($result);
} else {
$name = "";
}
?>
<form method="POST" action="categorie.php">
<div>
<input type="hidden" name="category_id" value="<?php echo $category_id ?>"/>
<input type="hidden" name="new" value="<?php echo $id?>"/>
<table>
<tr>
<td><label for="name">Category name:</label></td>
<td><input type="text" name="name" id="name" value="<?php echo $name ?>"/></td>
</tr>
<tr>
<td><label for="moderator">Moderator:</label></td>
<td><select name="moderator">
<?php
$sql2 = "SELECT user_id, username FROM user WHERE type_id = 1 ";
$rs2 = mysql_query($sql2);
while(list($user_id, $username) = mysql_fetch_array($rs2)){
?>
<option value="<?php echo $user_id ?>"><?php echo $username ?></option><?php } ?>
</select></td>
<tr>
<tr>
<td colspan="2"><input type="submit" value="Send" id="submit"/></td>
</tr>
</table>
</div>
</form>
<?php
mysql_close($dbc);
?>
</div>
</div><?php include("footer.php"); ?>
</body>
</html>