PHP，购物车程序出错

Question

我正在尝试在 PHP 中创建购物车。它运作良好。但后来我从购物车中删除了所有商品，但失败了。我认为它与 session 有关系，但我不完全确定。我收到此错误：

Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in C:\Apache24\htdocs\phpshop\index.php on line 85
Call Stack
#   Time    Memory  Function    Location
1   0.0002  244096  {main}( )   ...\index.php:0
2   0.0017  255352  mysqli_fetch_array ( )

I used this Shopping cart tutorial to build this program.

cart.php代码：

<?php



if(isset($_POST['submit']))
{

    foreach($_POST['quantity'] as $key => $val)
    {
        if($val==0)
        {
            unset($_SESSION['cart'][$key]);


        }
        else
        {
            $_SESSION['cart'][$key]['quantity']=$val;
        }
    }

}

?>

<h1>View cart</h1>
<a href="index.php?page=products">Go back to products page</a>
<form method="post" action="index.php?page=cart">

    <table>

        <tr>
            <th>Name</th>
            <th>Quantity</th>
            <th>Price</th>
            <th>Items Price</th>
        </tr>

        <?php

        $sql="SELECT * FROM products WHERE id_product IN (";

        foreach($_SESSION['cart'] as $id => $value)
        {
            $sql.=$id.",";
        }




        $sql=substr($sql, 0, -1).") ORDER BY name ASC";

第 85 行关于此处 ---> $query = mysqli_query($con,$sql);

        $totalprice=0;

        $numrows = mysqli_num_rows($query);

        if($numrows == 0)
        {

            header("Location: index.php");

        }

        while($row=mysqli_fetch_array($query))
        {
            $subtotal=$_SESSION['cart'][$row['id_product']]['quantity']*$row['price'];
            $totalprice+=$subtotal;
            ?>
            <tr>
                <td><?php echo $row['name'] ?></td>
                <td><input type="text" name="quantity[<?php echo $row['id_product'] ?>]" size="5" value="<?php echo $_SESSION['cart'][$row['id_product']]['quantity'] ?>" /></td>
                <td><?php echo $row['price'] ?>$</td>
                <td><?php echo $_SESSION['cart'][$row['id_product']]['quantity']*$row['price'] ?>$</td>
            </tr>
            <?php

        }
        ?>
        <tr>
            <td colspan="4">Total Price: <?php echo $totalprice ?></td>
        </tr>

    </table>
    <br />
    <button type="submit" name="submit">Update Cart</button>
</form>
<br />
<p>To remove an item, set it's quantity to 0. </p>

index.php

<?php




session_start();









require("includes/connection.php");
if(isset($_GET['page'])){

    $pages=array("products", "cart");

    if(in_array($_GET['page'], $pages)) {

        $_page=$_GET['page'];

    }else{

        $_page="products";

    }

}
else{

    $_page="products";

}
?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head>

    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <link rel="stylesheet" href="css/reset.css" />
    <link rel="stylesheet" href="css/style.css" />

    <title>Shopping cart</title>

</head>

<body>

<div id="container">

    <div id="main">

        <?php require($_page.".php"); ?>

    </div><!--end main-->

    <div id="sidebar">

        <h1>Cart</h1>
        <?php

        if(isset($_SESSION['cart'])){

            $sql="SELECT * FROM products WHERE id_product IN (";

            foreach($_SESSION['cart'] as $id => $value)
            {
                $sql.=$id.",";
            }







            $sql=substr($sql, 0, -1).") ORDER BY name ASC";
            $query = mysqli_query($con,$sql);
            while($row=mysqli_fetch_array($query))
            {

                ?>
                <p><?php echo $row['name'] ?> x <?php echo $_SESSION['cart'][$row['id_product']]['quantity'] ?></p>
                <?php

            }
            ?>
            <hr />
            <a href="index.php?page=cart">Go to cart</a>
            <?php

        }
        else
        {

            echo "<p>Your Cart is empty. Please add some products.</p>";

        }

        ?>

    </div><!--end sidebar-->

</div><!--end container-->

</body>
</html>

products.php

<?php



if(isset($_GET['action']) && $_GET['action']=="add")
{

    $id=intval($_GET['id']);

    if(isset($_SESSION['cart'][$id])){

        $_SESSION['cart'][$id]['quantity']++;

    }

    else
    {

        $sql_s="SELECT * FROM products WHERE id_product={$id}";

        $query_s=mysqli_query($con,$sql_s);

        if(mysqli_num_rows($query_s)!=0)
        {
            $row_s=mysqli_fetch_array($query_s);

            $_SESSION['cart'][$row_s['id_product']]=array
            (
                "quantity" => 1,
                "price" => $row_s['price']
            );


        }
        else
        {

            $message="This product id it's invalid!";

        }

    }

}

?>

<h1>Product List</h1>

<?php
if(isset($message)){
    echo "<h2>$message</h2>";
}
?>
<table>
    <?php

    $sql = "SELECT * FROM products ORDER BY name ASC";
    $query = mysqli_query($con,$sql);

    while ($row=mysqli_fetch_array($query)) {

        ?>
        <tr>
            <td><?php echo $row['name'] ?></td>
            <td><?php echo $row['description'] ?></td>
            <td><?php echo $row['price'] ?>$</td>
            <td><a href="index.php?page=products&action=add&id=<?php echo $row['id_product'] ?>">Add to cart</a></td>
        </tr>
        <?php

    }

    ?>
</table>

Answer 1

你的作业

$query = mysqli_query($con,$sql);

失败并返回布尔值 FALSE。这是因为 $con 设置不正确。

http://php.net/manual/en/mysqli.query.php

因此，您将 FALSE 作为 $query

传递给 mysqli_fetch_array

while($row=mysqli_fetch_array($query))

这是导致您报告的错误的原因

警告：mysqli_fetch_array() 期望参数 1 为 mysqli_result，第 85 行 C:\Apache24\htdocs\phpshop\index.php 中给出的布尔值

PHP，购物车程序出错

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