Question

我正在为网站制作购物车功能，并偶然发现了这个错误：

致命错误：第77行的......中不支持的操作数类型

我认为这可能是因为我在变量和数组中的值之间执行一些数学运算。我不确定如何对数组中的值执行数学运算：

($line_cost = $price * $quantity).

有人可以给我任何指导吗？我将万分感激！这是我的代码 -

<?php session_start(); ?>

<?php

    $product_id = $_GET['id'];   //the product id from the URL 
    $action     = $_GET['action']; //the action from the URL 

    //if there is an product_id and that product_id doesn't exist display an error message
    if($product_id && !productExists($product_id)) {
        die("Error. Product Doesn't Exist");
    }

    switch($action) {   //decide what to do 

        case "add":
            $_SESSION['cart'][$product_id]++; //add one to the quantity of the product with id $product_id 
        break;

        case "remove":
            $_SESSION['cart'][$product_id]--; //remove one from the quantity of the product with id $product_id 
            if($_SESSION['cart'][$product_id] == 0) unset($_SESSION['cart'][$product_id]); //if the quantity is zero, remove it completely (using the 'unset' function) - otherwise is will show zero, then -1, -2 etc when the user keeps removing items. 
        break;

        case "empty":
            unset($_SESSION['cart']); //unset the whole cart, i.e. empty the cart. 
        break;

    }

?>


<?php   

    if($_SESSION['cart']) { //if the cart isn't empty
        //show the cart

        echo "<table border=\"1\" padding=\"3\" width=\"40%\">";    //format the cart using a HTML table

            //iterate through the cart, the $product_id is the key and $quantity is the value
            foreach($_SESSION['cart'] as $product_id => $quantity) {    

                //get the name, description and price from the database - this will depend on your database implementation.
                //use sprintf to make sure that $product_id is inserted into the query as a number - to prevent SQL injection
                $sql = sprintf("SELECT name, description, price FROM php_shop_products WHERE id = %d;",
                                $product_id); 

                $result = mysql_query($sql);

                //Only display the row if there is a product (though there should always be as we have already checked)
                if(mysql_num_rows($result) > 0) {

                    list($name, $description, $price) = mysql_fetch_row($result);

                echo "$price";
                var_dump($quantity);

                    $line_cost = $price * $quantity;        //work out the line cost
                    $total = $total + $line_cost;           //add to the total cost

                    echo "<tr>";
                        //show this information in table cells
                        echo "<td align=\"center\">$name</td>";
                        //along with a 'remove' link next to the quantity - which links to this page, but with an action of remove, and the id of the current product
                        echo "<td align=\"center\">$quantity <a href=\"$_SERVER[PHP_SELF]?action=remove&id=$product_id\">X</a></td>";
                        echo "<td align=\"center\">$line_cost</td>";

                    echo "</tr>";

                }

            }

            //show the total
            echo "<tr>";
                echo "<td colspan=\"2\" align=\"right\">Total</td>";
                echo "<td align=\"right\">$total</td>";
            echo "</tr>";

            //show the empty cart link - which links to this page, but with an action of empty. A simple bit of javascript in the onlick event of the link asks the user for confirmation
            echo "<tr>";
                echo "<td colspan=\"3\" align=\"right\"><a href=\"$_SERVER[PHP_SELF]?action=empty\" onclick=\"return confirm('Are you sure?');\">Empty Cart</a></td>";
            echo "</tr>";       
        echo "</table>";



    }else{
        //otherwise tell the user they have no items in their cart
        echo "You have no items in your shopping cart.";

    }

    //function to check if a product exists
    function productExists($product_id) {
            //use sprintf to make sure that $product_id is inserted into the query as a number - to prevent SQL injection
            $sql = sprintf("SELECT * FROM php_shop_products WHERE id = %d;",
                            $product_id); 

            return mysql_num_rows(mysql_query($sql)) > 0;
    }
?>

<a href="products.php">Continue Shopping</a>


<?php

/*

products table:
    CREATE TABLE `products` (
        `id` INT NOT NULL AUTO_INCREMENT ,
        `name` VARCHAR( 255 ) NOT NULL ,
        `description` TEXT,
        `price` DOUBLE DEFAULT '0.00' NOT NULL ,
        PRIMARY KEY ( `id` )
    );

*/

?>



</body>
</html>

Answer 1

由于gettype()函数显示$price是一个字符串而$quantity是一个数组，首先将类型$price转换为整数并使用数组$quantity它是访问整数值的关键（如果它不是整数，也可以对它进行类型转换）。

所以它就像：

$line_cost =(int)$price * (int)$quantity['key'];

希望它有效！

不支持的操作数类型

1 个答案: