PHP updates the shopping cart quantity of form part and PHP processing part

Form section:

 
<form action="?action=edit_num" method="post" name="car<?php $c_rs['id'];?>" id="car<?php $c_rs['id'];?>"> 
<input name="suliang[<?php echo $c_rs['sp_id'];?>]" type="text" id="suliang[<?php echo $c_rs['sp_id'];?>]" value="<?php echo $c_rs['suliang'];?>"/> 
<input type="submit" name="button" id="button" value=" Update shopping cart " /> 
</form> 

PHP processing part:

 
<?php 
require 'config.inc.php'; 
require 'checklogin.php'; 
$username = $_SESSION['username']; 
$action = $_GET['action']; 
switch ($action) { 
case "edit_num": 

$arr = $arr = $_POST['suliang']; 
foreach($arr as $key=>$value){ 
$sqlgx = "update `cartemp` set suliang='$value' where username='".$username."' and flag=0 and sp_id='".$key."'"; 
mysql_query($sqlgx, $conn); 
echo "<script>location.href='shopcat.php'</script>"; 
} 
break; 

case "null": 
$null_sql = "delete from `cartemp` where username='$username' and flag=0 "; 
mysql_query($null_sql, $conn); 
echo "<script>location.href='shopcat.php'</script>"; 
break; 
case "del": 
$id = $_GET['id']; 
$del_sql = "delete from `cartemp` where id=$id"; 
mysql_query($del_sql, $conn); 
echo "<script>location.href='shopcat.php'</script>"; 
break; 
} 
?>