Kosárba helyezés tutoriallal elakadtam egy kicsit, mit nem csináltam jól?

kosarba.php:

<?php

if(isset($_POST["kosarba"])){

if(!empty($_POST["termekid"])){

$termekid = $_POST["termekid"];

if(isset($_POST["db"])){

$db = $_POST["db"];

if($_POST["db"] > 0){

if(isset($_SESSION["kosar"][$termekid])){

$_SESSION["kosar"][$termekid] = $_SESSION["kosar"][$termekid]+$db;

}else{

$_SESSION["kosar"][$termekid]=$db;

}

}

}

}

}

echo "<pre>";

echo($_SESSION["kosar"]);

echo "</pre>";

?>

index.php:

<?php

session_start();

include 'kosarba.php';

$conn=mysql_connect("localhost", "valami", "pw");

if (!$conn) {

die ("<tr><td colspan=3 align='center'><font color=#FF0000>MySQL hiba</font>" . mysql_error());

}

mysql_select_db("db");

mysql_query("set names latin2");

$res=mysql_query("SELECT * FROM telefonok LIMIT 1,3");

while($sor=mysql_fetch_row($res))

if($telo%2==0)

echo"

<div class='item'>

<a href='reszletek.php?telefonid=$sor[0]'><img src='$sor[4]' alt='$sor[1]' width='110' height='170' /></a>

<a href='reszletek.php?telefonid=$sor[0]' class='name'>$sor[5] $sor[1]</a>

<span>$sor[3] Ft</span>

<form method='post'>

<input type='hidden' name='termekid' value=".$a['termekid'].">

<input type='text' size='3' name='db' value=''>darabot

<input type='submit' value='kosárba' name='kosarba'>

</form>

</div>";

echo "<p>";

for($i=1;$i<=$lapok_szama;$i++)

echo "<a href='akcio.php?page=$i'>$i oldal</a> ";

echo "</p>";

$telo++;

?>