我在php中添加了购物车代码。我创建了一个代码，当用户在购物车中选择一个现有产品时，现有产品的数量和输入的新数量将相互添加
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "pos";
$id=$name =$price=$quantity_order=$old_quantity_order = "";
$conn = mysqli_connect($servername, $username, $password, $dbname);
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$id = $_POST['id'];
$name = $_POST['name'];
$price = $_POST['price'];
$quantity_order = $_POST['quantity_order'];
$subtotal = $price * $quantity_order;
}
$check="SELECT * FROM cart WHERE id = $id";
$sql = mysqli_query($conn,$check) or die(mysql_error());
if (mysqli_num_rows($sql) > 0) {
while($res = mysqli_fetch_row($sql))
{
$old_quantity_order=$res['quantity_order'];
}
$new_quantity_order =$quantity_order + $old_quantity_order;
$up = mysqli_query($conn, "UPDATE cart SET quantity_order='$new_quantity_order' WHERE id=$id");
}
else {
$sql =mysqli_query($conn,"INSERT INTO cart (id,name, price,quantity_order,subtotal)
VALUES ('$id', '$name', '$price','$quantity_order','$subtotal')");
}
header("Location:pos.php")
我试图获取数据库中的现有数量并将其重命名为$ old_quantity_order，然后将其添加到输入的数量中，即$ quantity_order。
但是进入我的数据库的唯一值是$ quantity_order的值，$ old_quantity_order是0。
这是我用来向购物车添加订购数量的表格。
<div class="form-group">
<form method="post">
<input type="hidden" name="id" value="<?php echo $id; ?>"/>
<input type="hidden" name="name" value="<?php echo $name; ?>"/>
<input type="hidden" name="price" value="<?php echo $price; ?>"/>
<input type="hidden" name="quantity" value="<?php echo $quantity; ?>"/>
<label>Quantity</label>
<input class="form-control" type="number" name="quantity_order" placeholder="quantity" min="1" max="<?php echo $quantity; ?>" />
<input class="btn btn-primary" type="submit" name="add_to_cart" formaction="add_to_cart.php" id="add_to_cart" value="Add to Cart" OnClick="return mess();">
<input class="btn btn-success" type="submit" name="process" formaction="process_frompos.php" value="Process"></a>
</form>
</div>
答案 0 :(得分：0)
运行以下代码，看看是否有PHP Errors。
$servername = "localhost";
//it is BAD practise to connect to your DB as root.
$username = "pubuser";
$password = "";
$dbname = "pos";
$id = $price = $quantity_order = $old_quantity_order = 0;
$name = "";
$conn = mysqli_connect($servername, $username, $password, $dbname);
//
// $_SERVER["REQUEST_METHOD"] is so common, and I don't like it as it's
// not a clear check. Intead check that the array is populated.
//
if (\is_array($_POST) && \count($_POST) > 0) {
// Id is usually a digit number.
// So force to type. NEVER trust user input!
$id = (int) $_POST['id'];
$name = $_POST['name'];
// $price may be a float or an int?
$price = (float) $_POST['price'];
$quantity_order = (int) $_POST['quantity_order'];
$subtotal = $price * $quantity_order;
}
//
// So what happens here, if POST has not been set?
//
// Only grab the rows you need from the database:
$check="SELECT quantity_order FROM cart WHERE id = $id";
// 1) Mysqli_error needs the connection variable.
// 2) Errors shold be logged to an error log, NOT thrown to output.
// 3) USE PREPARED STATEMENTS
$sql = mysqli_query($conn,$check) or error_log(__LINE__." : ".mysqli_error($conn));
if (mysqli_num_rows($sql) > 0) {
// Because you're calling only one row, you don't need to loop it.
$res = mysqli_fetch_row($sql);
$new_quantity_order = $quantity_order + $res['quantity_order'];
$up = mysqli_query($conn, "UPDATE cart SET quantity_order =
".(int)$new_quantity_order." WHERE id = ".$id );
}
else {
// Numerical column values in SQL do not need to be encased in quotes
// and this slows down transactions.
$sql = "INSERT INTO cart (id, name, price, quantity_order, subtotal)
VALUES ( ".$id.", '".$name."', ".$price.", ".(int)$quantity_order." ,".$subtotal.")";
mysqli_query($conn, $sql) or error_log(__LINE__." : ".mysqli_error($conn));
}
// your header needs to have a semicolon ; at the end.
header("Location:pos.php");
// header Locations MUST then be followed by an exit/die statement.
exit;