我是php新手，我正在将脚本从使用mysql_ *更改为mysqli_ *函数。切换后我收到以下错误：
Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, null given in cart.php on line 115
Warning: mysqli_query() expects parameter 1 to be mysqli, null given in cart.php on line 115
我的代码
<title>Cart</title>
<?php
require("../mysqli_connect.php");
?>
</head>
<body>
<?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 products WHERE id = %d;",
$product_id);
$result = mysqli_query($dbc, $sql);
//Only display the row if there is a product (though there should always be as we have already checked)
if(mysqli_num_rows($result) > 0) {
list($name, $description, $price) = mysqli_fetch_row($result);
$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 products WHERE id = %d;",
$product_id);
return mysqli_num_rows(mysqli_query($dbc, $sql)) > 0; ***//this is line 15***
}
?>
<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>
这是产品页面。
<title>Products</title>
<?php
require("../mysqli_connect.php");
?>
</head>
<body>
<table border="1">
<?php
$sql = "SELECT id, name, description, price FROM products;";
$result = mysqli_query($dbc, $sql);
while(list($id, $name, $description, $price) = mysqli_fetch_row($result)) {
echo "<tr>";
echo "<td>$name</td>";
echo "<td>$description</td>";
echo "<td>$price</td>";
echo "<td><a href=\"cart.php?action=add&id=$id\">Add To Cart</a></td>";
echo "</tr>";
}
?>
</table>
<a href="cart.php">View Cart</a>
</body>
</html>
数据库连接
DEFINE ('DB_USER', 'username');
DEFINE ('DB_PASSWORD', 'password');
DEFINE ('DB_HOST', 'localhost');
DEFINE ('DB_NAME', 'domain_user');
// Make the connection:
$dbc = @mysqli_connect (DB_HOST, DB_USER, DB_PASSWORD, DB_NAME) OR die ('Could not connect to MySQL: ' . mysqli_connect_error() );
// Set the encoding...
mysqli_set_charset($dbc, 'utf8');
答案 0 :(得分：0)
您的连接未进入该功能。快速解决方法是在函数中标记变量GLOBAL。
function productExists($product_id) {
GLOBAL $dbc;
$sql = sprintf("SELECT * FROM products WHERE id = %d;", $product_id);
return mysqli_num_rows(mysqli_query($dbc, $sql)) > 0;
}
这种方式$dbc在您的函数中可用。
你可能想帮助让它更具可读性（至少在我看来......）
function productExists($product_id) {
GLOBAL $dbc;
$sql = sprintf("SELECT * FROM products WHERE id = %d;", $product_id);
$result = mysqli_query($dbc, $sql) or die(mysqli_error($dbc));
$rows = mysqli_num_rows($result);
return $rows;
}
我发现更容易阅读两行代替将函数嵌套到一行。