flow.dwt 部分

<script type="text/javascript" charset="utf-8">
function add_num(rec_id,goods_id)
{
	document.getElementById("goods_number_"+rec_id+"").value++;
	var number = document.getElementById("goods_number_"+rec_id+"").value;
	Ajax.call('flow.php', 'step=update_group_cart&rec_id=' + rec_id +'&number=' + number+'&goods_id=' + goods_id, changePriceRespone, 'GET', 'JSON');
}
function red_num(rec_id,goods_id)
{
	if (document.getElementById("goods_number_"+rec_id+"").value>1)
	{
		document.getElementById("goods_number_"+rec_id+"").value--;
	}
	var number = document.getElementById("goods_number_"+rec_id+"").value;
	Ajax.call('flow.php', 'step=update_group_cart&rec_id=' + rec_id +'&number=' + number+'&goods_id=' + goods_id, changePriceRespone, 'GET', 'JSON');
}
function change_price(rec_id,goods_id)
{
	var number = document.getElementById("goods_number_"+rec_id+"").value;
	//alert(number);
	Ajax.call('flow.php','step=update_group_cart&rec_id=' + rec_id +'&number=' + number+'&goods_id=' + goods_id, changePriceRespone, 'GET', 'JSON');
}
function changePriceRespone(result)
{
	if(result.error == 1)
	{
		alert(result.content);
		document.getElementById("goods_number_"+result.rec_id+"").value =result.number;
	}
	else
	{
		// 注意这里可能需要根据模板修改 !
		document.getElementById('subtotal_'+result.rec_id).innerHTML = result.subtotal;//商品总价
		document.getElementById('cart_amount_desc').innerHTML = result.cart_amount_desc;//购物车商品总价说明
		document.getElementById('market_amount_desc').innerHTML = result.market_amount_desc;//购物车商品总市价说明
	}
}
</script>


在购物车的商品数量处
<a href="javascript:;" onclick="red_num({$goods.rec_id},{$goods.goods_id});"> - </a>
<input type="text" name="goods_number[{$goods.rec_id}]" id="goods_number_{$goods.rec_id}" value="{$goods.goods_number}" size="4" class="inputBg" style="text-align:center " onblur="change_price({$goods.rec_id},{$goods.goods_id})"/>
<a href="javascript:;" onclick='add_num({$goods.rec_id},{$goods.goods_id})' >+</a>


flow.php 部分

elseif($_REQUEST['step']=='update_group_cart')
{  
	include_once('includes/cls_json.php');
	$result = array('error' => 0, 'message' => '', 'content' => '', 'goods_id' => '');
	$json = new JSON;
	$rec_id = $_GET['rec_id'];
	$number = $_GET['number'];
	$goods_id = $_GET['goods_id'];
	$result['rec_id'] = $rec_id;
	if ($GLOBALS['_CFG']['use_storage'] == 1)
	{
		$goods_number = $GLOBALS['db']->getOne("select goods_number from ".$GLOBALS['ecs']->table('goods')." where goods_id='$goods_id'");
		if($number>$goods_number)
		{
			$result['error'] = '1';
			$result['content'] ='对不起,您选择的数量超出库存您最多可购买'.$goods_number."件";
			$result['number']=$goods_number;
			die($json->encode($result));
		}
	}
	$sql = "UPDATE " . $GLOBALS['ecs']->table('cart') . " SET goods_number = '$number' WHERE rec_id = $rec_id";
	$GLOBALS['db']->query($sql);
	/* 取得商品列表，计算合计 */
	$cart_goods = get_cart_goods();
	$subtotal = $GLOBALS['db']->getONE("select goods_price * goods_number AS subtotal from ".$GLOBALS['ecs']->table('cart')." where rec_id = $rec_id");
	$result['subtotal'] = price_format($subtotal, false);
	$result['cart_amount_desc'] = sprintf($_LANG['shopping_money'], $cart_goods['total']['goods_price']);
	$result['market_amount_desc'] = sprintf($_LANG['than_market_price'], $cart_goods['total']['market_price'], $cart_goods['total']['saving'], $cart_goods['total']['save_rate']
	);
	die($json->encode($result));
}