PHP kodum çalışmıyor lütfen yardım '!

<?php

function UrunleriYukle() {
global $urun_listesi;

$dosyaadi = 'urun.txt';

$dosyaya_baglanti = @fopen($dosyaadi, "r");

while ($satir = fgets($dosyaya_baglanti, 1024)) {

list($id, $isim, $aciklama, $fiyat) = explode('|', $satir);
$id = trim($id);

$urun_listesi[$id] = array ("isim" => $isim, "aciklama" =>$aciklama, "fiyat" =>
$fiyat); }

@fclose($dosyaya_baglanti); }
?>

<?php 
require 'site_kut.inc.php';

UrunleriYukle();


$secilen_urun = array();


foreach ($urun_listesi as $urun_id => $urun) { if (trim($urun_id) == trim($id)) { $secilen_urun = $urun; } }

session_register('sepet');

if ($ordered) {  array_push($sepet[urunler], array(trim($id),
$miktar)); $sepet[urun_sayisi] += $miktar; }
?>
<html><head><title><?php if ($ordered) { ?> Urun <?php echo
$secilen_urun[isim]; ?> sepetime ekle <?php } else { ?> Sectigim <?php echo
$secilen_urun[isim]; ?> isimli urunu sepetime ekle
<?php } ?>
</title></head><body><?php if ($ordered) { ?><h1>
<?php
echo $secilen_urun[isim]; ?> isimli urun sepetinize basarili sekilde
eklendi.Tessekkur Ederiz.</h1>

Geriye <a href="sepet.php">donerek</a>alisverise devam edebilirsiniz.
<?php } else { ?>

<h1>Urunu <?php $secilen_urun[isim]; ?> sepetime ekle</h1>

<form action="<?php echo $PHP_SELF; ?>" method="GET"> Urun Ismi : <?php
echo $secilen_urun[isim]; ?> <BR> Urun Aciklamasi: <?php echo
$secilen_urun[aciklama]; ?> <BR> Urun Fiyati: <?php echo $secilen_urun[fiyat];
?> TL.

<BR> Urun Miktari: <input type="text" name="miktar"> <input
type="hidden" name="id" value="<?php echo $id; ?>"> <input type="hidden" name="ordered" value="1">
<input type="submit" value="Sepetime Ekle"> </form> <?php } ?>
</body></html>

<?php

require 'site_kut.inc.php';


session_register('sepet');

if (!isset($sepet[urun_sayisi])) { $sepet = array("urun_sayisi" => 0, "urunler" =>
array());
} 
UrunleriYukle();
?>
<html><head><title>Serkan`in Oyuncakci Dukkani</title></head><body>
<h1>Serkan`in Oyuncakci Dukkanina Hosgeldiniz :)</h1>
<?php if ($sepet[urun_sayisi]) { //sepetin icinde gosterilebilcek bir urun varsa, ?>
<h2>Sepetinizdeki Urunler:</h2>
<br><table border="2" cellpadding="5" cellspacing="2">
<tr><th>Urun Adi</th><th>Kisa Aciklama</th>
<th>Fiyat</th><th>Miktar</th><th></th></tr>
<?php
foreach ($sepet[urunler] as $i => $urun) { $urun_id = $urun[0]; $miktar =
$urun[1];

$toplam += $miktar * (double)$urun_listesi[$urun_id][fiyat];
?>
<tr><td><?php
echo $urun_listesi[$urun_id][isim];
?>
</td><td>
<?php
echo $urun_listesi[$urun_id][aciklama];
?> </td> <td>
<?php
echo
$urun_listesi[$urun_id][fiyat];
?></td><td><form action="miktar_degistir.php"
method="GET"> <input type="hidden" name="id" value="<?php echo $i; ?>">
<input type="text" name="miktar" value="<?php echo $miktar; ?>">
</td><td>
<input type="submit" value="Miktari Degistir"> </form>
</td> </tr>
<?php } ?><tr><td colspan="2"> Toplam Hesap Tutari : </td> <td
colspan="2">
<?php
echo $toplam; ?> TL </td></tr></table>
<BR>
<BR>
<?php } ?>
<h2> ..:: Serkan`in Oyuncakci Dukkani ::..</h2> <BR>

Online magazamizdan alabileceginiz oyuncaklarimiz:

<table border="2" cellpadding="5" cellspacing="2"> 
<tr><th>Urun Ismi</th><th>Urun Aciklamasi</th><th>Urun Fiyati</th><th></th></tr>
<?php
foreach ($urun_listesi as $urun_id => $oge) {
?>
<tr><td><?php
echo $oge[isim];
?>
</td><td><?php
echo $oge[aciklama];
?>
</td><td><?php
echo $oge[fiyat];
?>
</td><td>
<a href="sepete_at.php?id=<?php echo $urun_id; ?>"> Bu urunu sepetime ekle.
</a> </td> </tr> <?php } ?> </table></body></html>

<?php

session_register(`sepet`);


$i = (int)$id;


$eski_miktar = $sepet[urunler][$i][1]; if ($miktar) { $sepet[urunler][$i][1] =
$miktar; } else { unset($sepet[urunler][$i]);
}
$sepet[urun_sayisi] = ($eski_miktar > $miktar) ? $sepet[urun_sayisi] - ($eski_miktar-$miktar) : $sepet[urun_sayisi] + ($miktar-$eski_miktar);
?>
<html><head><title>Miktar Degistirme</title></head><body>
<h1>Urun miktari,
<?php
echo $eski_miktar; ?> den/dan
<?php
echo $miktar; ?>
olarak degistirildi...</h1>

Geri <a href="sepet.php">donerek</a> alisverise devam edebilirsiniz.
</body></html>

KOD101|Bisiklet|Dunyanin en saglikli nakil araci|125 
KOD102|Oyuncak Telsiz|2 Km ye kadar etkili araci|380