Question

我还是php的新手（昨天才刚开始），当我想删除我的数据时，它会显示
Notice: Undefined index: bookname in C:\wamp64\www\HelpingClass\delete.php on line 13
Notice: Undefined index: quantity in C:\wamp64\www\HelpingClass\delete.php on line 14
Notice: Undefined index: price in C:\wamp64\www\HelpingClass\delete.php on line 15

这是我在第13,14,15行的代码

$bookname = $_POST['bookname'];
$quantity = $_POST['quantity'];
$price = $_POST['price'];

我什至尝试将这些13,14,15行更改为此

    if(isset($_POST['bookname']) && isset($_POST['bookname'])){
    echo $_POST['bookname'];
}
    if(isset($_POST['quantity']) && isset($_POST['quantity'])){
    echo $_POST['quantity'];
}
    if(isset($_POST['price']) && isset($_POST['price'])){
    echo $_POST['price'];}

通知未定义索引不见了，但我仍然无法删除数据:(

这是我的delete.php完整代码

<?php
    include ('connection.php');
    session_start();
    if (!isset($_SESSION ['userid'])&& empty($_SESSION['userid'])){
        header ("location:login.php");
        exit;
    }
    else {
        $userid = $_SESSION ['userid'];
    }

    $bookid = $_GET['bookid'];
    $bookname = $_POST['bookname'];
    $quantity = $_POST['quantity'];
    $price = $_POST['price'];

    $query = mysqli_query ($conn, "DELETE FROM book SET WHERE Book_Id='$bookid';");

    if ($query == TRUE)
        {
            echo "<script language='javascript'>";
            echo "alert('Deleted.');";
            echo "window.location.href='action.php';";
            echo "</script>";
        }
        else
        {
            echo "<script language='javascript'>";
            echo "alert('Delete Failed.');";
            //echo "window.location.href='action.php';";
            echo "</script>";
        }


 ?>

非常感谢您的帮助

Answer 1

您的代码中有很多问题。

最重要，您的数据库查询对SQL Injection相关问题开放。请使用Prepared Statements。

参数化版本的示例可能是：

// prepare the query statement
$stmt = $mysqli_prepare($conn, "DELETE FROM book 
                                WHERE Book_Id = ?");
// bind the parameters
$stmt->bind_param("i", $bookid);
// execute the query
$stmt->execute();
//fetching result would go here (in case of SELECT queries)
$stmt->close();

其次，使用isset函数检查变量是否存在。您可以在旁边使用三元运算符。

例如：

$bookid = isset($_GET['bookid']) ? $_GET['bookid'] : 0;
$bookname = isset($_POST['bookname']) ? $_POST['bookname'] : '';
$quantity = isset($_POST['quantity']) ? $_POST['quantity'] : 0;
$price = isset($_POST['price']) ? $_POST['price'] : 0;

第三，您的DELETE查询语句语法错误。您不能使用*和SET。另外，在(int)上进行$bookid类型转换（假设此处为整数）。使用;函数时，查询字符串中也不需要分号（mysqli_query）。

应如下所示：

$query = mysqli_query ($conn, "DELETE FROM book 
                               WHERE Book_Id = '" . (int)$bookid . "'");

在MySQL Documentation中，DELETE语句的语法如下：

DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name
    [PARTITION (partition_name [, partition_name] ...)]
    [WHERE where_condition]
    [ORDER BY ...]
    [LIMIT row_count]

在PHP中删除的未定义索引

1 个答案: