Fout in query

<?php
$host           =    "****";   // host waarop mysql draait
$user           =    "*****";  // gebruiker
$pass           =    "****";	// wachtwoord van gebruiker
$db             =    "*****";	// database om te gebruiken
mysql_connect($host, $user, $pass) or die (mysql_error());
mysql_select_db($db) or die (mysql_error());

setcookie("userid", "1", time()+3600, "/");



if(isset($_POST['koop']))
{

function koop()
{
global $wapen;
global $aantal;
$koop = mysql_query("UPDATE wapens SET ".$wapen."='".$aantal."' WHERE user_id='".$_COOKIE['userid']."'") or die(mysql_error());
if(!@mysql_query($koop) or die(mysql_error()))
{
echo "Query mislukt.";
}
else {
echo "Gelukt!";
}
return $koop;
}

$wapen = $_POST['wapen'];
$getal1 = $_POST['aantal'];

$aantal = $getal1;

koop();
}
else { 
?>
<form action="<?=$PHP_SELF; ?>" method="POST">
<fieldset>
wapen:<Br />
<input type="text" name="wapen">
aantal:<Br />
<input type="text" name="aantal">
<input type="submit" name="koop" value="Doe aankopen!" />
</fieldset>
</form>
<?
}
?>

<?php
$host           =    "****";   // host waarop mysql draait
$user           =    "*****";  // gebruiker
$pass           =    "****";	// wachtwoord van gebruiker
$db             =    "*****";	// database om te gebruiken
mysql_connect($host, $user, $pass) or die (mysql_error());
mysql_select_db($db) or die (mysql_error());
 
setcookie("userid", "1", time()+3600, "/");
 
 
 
if(isset($_POST['koop']))
{
 
function koop()
{
global $wapen;
global $aantal;
$koop = mysql_query("UPDATE wapens SET ".$wapen."='".$aantal."' WHERE user_id='".$_COOKIE['userid']."'") or die(mysql_error());
if(!@mysql_query($koop) or die(mysql_error()))
{
echo "Query mislukt.";
}
else {
echo "Gelukt!";
}
return $koop;
}
 
$wapen = $_POST['wapen'];
$getal1 = $_POST['aantal'];
 
$aantal = $getal1;
 
koop();
}
else { 
?>
<form action="<?=$PHP_SELF; ?>" method="POST">
<fieldset>
wapen:<Br />
<input type="text" name="wapen">
aantal:<Br />
<input type="text" name="aantal">
<input type="submit" name="koop" value="Doe aankopen!" />
</fieldset>
</form>
<?
}
?>

<? echo "UPDATE wapens SET ".$wapen."='".$aantal."' WHERE user_id='".$_COOKIE['userid']."'"; ?>

<? echo "UPDATE wapens SET ".$wapen."='".$aantal."' WHERE user_id='".$_COOKIE['userid']."'"; ?>

$koop = mysql_query("UPDATE wapens SET ".$wapen."='".$aantal."' WHERE user_id='".$_COOKIE['userid']."'") or die(mysql_error());
if(!@mysql_query($koop) or die(mysql_error()))
{
echo "Query mislukt.";
}

$koop = mysql_query("UPDATE wapens SET ".$wapen."='".$aantal."' WHERE user_id='".$_COOKIE['userid']."'") or die(mysql_error());
if(!@mysql_query($koop) or die(mysql_error()))
{
echo "Query mislukt.";
}