购物车问题？

<?php 
session_start(); 
require("mywebmanage/conn.php");
 if($_SESSION[username]==""){
    echo "<script>alert('请先登录，后购物!');history.back();</script>";
exit; }  
?>
<table width="100%" border="0" cellspacing="0" cellpadding="0">
 <?
$_session['total'];
$arraygwc=explode("@",$_SESSION[producelist]);$s=0;
 for($i=0;$i<count($arraygwc);$i++){
  $s+=intval($arraygwc[$i]);
 }
 if($s==0){
         echo "<tr>";
         echo" <td colspan='5'>您的购物车为空!</td>";
         echo"</tr>";
 
 }
 else
 {
?> 
<tr>
    <td>数量</td>
    <td>名称</td>
    <td>价格</td>
    <td>小计</td>
<td>操作</td>
  </tr>
<?
$total=0;
$array=explode("@",$_SESSION[producelist]);
$arrayquatity=explode("@",$_SESSION[quatity]);while(list($name,$value)=each($_POST)){
for($i=0;$i<count($array)-1;$i++){ if(($array[$i])==$name)
{
$arrayquatity[$i]=$value; 
}
}
$_SESSION[quatity]=implode("@",$arrayquatity);
//print_r($_SESSION[quatity]);
for($i=0;$i<count($array)-1;$i++){
$id=$array[$i];

$num=$arrayquatity[$i];
if($id!="")
{   
$sql=mysql_query("select * from casee where news_id=$id");
$array=mysql_fetch_array($sql);
$total1=$num*$array[price];
$news_title=$array[news_title];


$total+=$total1;
$_SESSION["total"]=$total;

?>
  <tr>
    <td>&nbsp;</td>
    <td><? echo $news_title;?></td>
    <td><? echo $array['price'];?></td>
    <td><? echo $total;?></td>
<td>移除</td>
  </tr>
      <?php
}
}
}
 
?>
  <tr>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
    <td>&nbsp;</td>
<td>&nbsp;</td>
  </tr>
</table>
<?php
}

?>
为什么在红的那一行就不执行了？为什么会条件不满足？？？求高手解答