不支持的操作数类型 [英] Unsupported operand types

问题描述

我正在为网站使用购物车功能，但偶然发现此错误:

I am working on a shopping cart function for a website and have stumbled across this error:

致命错误:第77行的...中不受支持的操作数类型

我认为这可能是因为我正在数组中的变量和值之间执行一些数学运算.我不确定如何在数组中的值上执行数学运算:

I think this may be because I am performing some math between a variable and a value within an array. What I am not sure of is how to perform math on a value within an array:

($line_cost = $price * $quantity). 

有人可以给我任何指导吗?我将不胜感激！这是我的代码-

Can anyone give me any guidance on this please? I will be most grateful! Here is my code -

<?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>

推荐答案

AS gettype()函数显示$price是字符串，而$quantity是数组，首先将$price转换为整数，然后使用该数组$quantity，其键用于访问整数值(如果它不是整数，则也进行类型转换).

AS the gettype() function shows that $price is a string and $quantity is an array, typecast $price first to integer and use the array $quantity with its key to access the integer value (if it is not an integer, typecast it too).

所以它像这样:

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

希望它能起作用！

这篇关于不支持的操作数类型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！