ขอความช่วยเหลือเรื่องการส่งค่าตัวแปรข้ามเพจ ด้วยคำสั่ง Onclick ด้วยครับ

<form action="process/cartUpdate.php" method="post">
<table class="list" width="100%" border="0" align="center" cellpadding="5" cellspacing="1">
  <tr>
    <th width="40" align="center">ลบ</th>
    <th width="100" align="center">ภาพสินค้า</th>
    <th align="center">รายการสินค้า</th>
    <th width="65" align="center">ราคา</th>
    <th width="65" align="center">จำนวน</th>
    <th width="75" align="center">ราคารวม</th>
  </tr>
<? 
    $i=0; 
    $sum=0;
    $quantity=0;
    foreach($cart as $id=>$item){ 
?>
  <tr>
    <td align="center">
      <input class="form" type="checkbox" name="remove[]" value="<?=$id?>" />
    </td>
    <td align="center">
      <a href="สินค้า-<?=$item['id']."-".rewrite_url($item['name'])?>.html" title="<?=$item['name']?>" target="_blank"><img src="product/<?=$item['image']?>" width="90" border="0"/></a>
    </td>
    <td align="center"><?=$item['name']?><br/><?=$item['option']?></td>
    <td align="center"><?=number_format($item['price'])?></td>
    <td align="center">
      <a href="javascript:;"onclick="del('<?=$i+1?>')" style="display:block; margin-bottom:5px;"><img src="image/icon-minus.gif" border="0"/></a>
      <input class="form" style="width:20px; text-align:center;" name="amount[<?=$id?>]" type="text" id="<?=$i+1?>" value="<?=$item['amount']?>"/>
      <a href="javascript:;" onclick="plus('<?=$i+1?>')" style="display:block;margin-top:5px;"><img src="<?=$rowSetting['website_name']."/"?>image/icon-plus.gif" border="0" /></a>
    </td>
    <td align="right"><?=number_format($item['price']*$item['amount'])?></td>
  </tr>
<? 	
    $sum+=$item['price']*$item['amount'];
    $quantity+=$item['amount'];
    $i++;
    }
?>
  <tr>
    <td colspan="5" align="right" style="background:#fafafa;">ราคารวม (บาท)</td>
    <td style="font-size:16px;background:#fafafa;" align="right"><?=number_format($sum)?></td>
  </tr>
<tr>
    <td colspan="6" align="right" style="background:#fafafa;">
<?php
$sqlFreeShipping="SELECT * FROM shipping WHERE id=1";
$resultFreeShipping=mysql_query($sqlFreeShipping)or die(mysql_error());
$rowFreeShipping=mysql_fetch_array($resultFreeShipping);
if($sum<=$rowFreeShipping['price']||$sum==0){
?>
เลือกวิธีจัดส่ง
<select name="shipping">
<?
  $sqlShipping="SELECT * FROM shipping WHERE id!=1";
  $resultShipping=mysql_query($sqlShipping)or die(mysql_error());
  $numShipping=mysql_num_rows($resultShipping);
  for($i=1;$i<=$numShipping;$i++){$rowShipping=mysql_fetch_array($resultShipping);
?>
  <option value="<?=$rowShipping['id']?>"><?=$rowShipping['option']?> &nbsp;&nbsp;<? if($rowShipping['price']>0){echo $rowShipping['price'].'บาท';}?></option>
  
<?
}
?>
</select>
<?
}
else{echo"$rowFreeShipping[option] <input type='hidden' name='shipping' value='1'/>";}
?>
    </td>
  </tr>
</table>
<div align="center" style="padding:15px 0 0 0;">
  <input type="button" onclick="window.location='รายการสินค้า-1.html';" value="เลือกสินค้าต่อ" />
  <input type="submit" class="button" value="คำนวณราคาสินค้าในตะกร้าใหม่" />
  <input type="button" class="button" onclick="window.location='จัดส่ง.html';" value="ดำเนินการสั่งซื้อ" />
</div>
</form>