if(! $session && ! $scid) {

$session = md5(uniqid(rand()));

SetCookie(scid, $session, time() + 14400);

}
class Cart { //开始购物车类
function check_item( $table, $session, $product) {

$query = SELECT * FROM $table WHERE session=' $session' AND product=' $product' ;

$result = mysql_query( $query);
if(! $result) {
return 0;
}

$numRows = mysql_num_rows( $result);
if( $numRows == 0) {
return 0;

} else {
$row = mysql_fetch_object( $result);
return $row->quantity;

}
}
function add_item( $table, $session, $product, $quantity) {

$qty = $this->check_item( $table, $session, $product);

if( $qty == 0) {
$query = INSERT INTO $table (session, product, quantity) VALUES ;
$query .= (' $session', ' $product', ' $quantity') ;
mysql_query( $query);

} else {
$quantity += $qty; //若有，则在原有基础上增加数量
$query = UPDATE $table SET quantity=' $quantity' WHERE session=' $session' AND ;
$query .= product=' $product' ;
mysql_query( $query);

}
}
function delete_item( $table, $session, $product) {

$query = DELETE FROM $table WHERE session=' $session' AND product=' $product' ;
mysql_query( $query);

}
function modify_quantity( $table, $session, $product, $quantity) {

$query = UPDATE $table SET quantity=' $quantity' WHERE session=' $session' ;
$query .= AND product=' $product' ;
mysql_query( $query);

}
function clear_cart( $table, $session) {

$query = DELETE FROM $table WHERE session=' $session' ;
mysql_query( $query);
}
function cart_total( $table, $session) {

$query = SELECT * FROM $table WHERE session=' $session' ;
$result = mysql_query( $query);

if(mysql_num_rows( $result) > 0) {
while( $row = mysql_fetch_object( $result)) {

$query = SELECT price FROM inventory WHERE product=' $row->product' ;
$invResult = mysql_query( $query);

$row_price = mysql_fetch_object( $invResult);
$total += ( $row_price->price * $row->quantity);
/*
总价 += 该物品价格 * 该物品数量
（ 大家应该能看明白吧 ）
*/
}
}
return $total; //返回总价钱
}
function display_contents( $table, $session) {

$count = 0;

$query = SELECT * FROM $table WHERE session=' $session' ORDER BY id ;
$result = mysql_query( $query);

while( $row = mysql_fetch_object( $result)) {

$query = SELECT * FROM inventory WHERE product=' $row->product' ;
$result_inv = mysql_query( $query);

$row_inventory = mysql_fetch_object( $result_inv);
$contents[product][ $count] = $row_inventory->product;
$contents[price][ $count] = $row_inventory->price;
$contents[quantity][ $count] = $row->quantity;
$contents[total][ $count] = ( $row_inventory->price * $row->quantity);
$contents[description][ $count] = $row_inventory->description;

$count++; //物品数量加一（即下一个物品）
}
$total = $this->cart_total( $table, $session);
$contents[final] = $total;

return $contents;

}
function num_items( $table, $session) {

$query = SELECT * FROM $table WHERE session=' $session' ;
$result = mysql_query( $query);
$num_rows = mysql_num_rows( $result);
return $num_rows;

}
function quant_items( $table, $session) {

$quant = 0;// 物品总量
$query = SELECT * FROM $table WHERE session=' $session' ;
$result = mysql_query( $query);
while( $row = mysql_fetch_object( $result)) {

$quant += $row->quantity; //该物品数量加到总量里去
}
return $quant; //返回总量
}
}