php - sql注入(inject)登录表单错误

Question

我正在编写有关如何使用旧 PHP 代码进行 SQL 注入(inject)的教程。我有我正在测试的这段代码，但我有一个错误说:

Fatal error: Call to a member function fetch_assoc() on a non-object

这是旧代码:

<?php
$host="localhost"; // Host name 
$username="root"; // Mysql username 
$password="root"; // Mysql password 
$db_name="graphic_db"; // Database name 
$tbl_name="login"; // Table name 
//if(!session_is_registered(myusername)){
//header("location:index.html");
  $con=mysqli_connect($host,$username,$password,$db_name);



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

    if($_POST['username'] != '' && $_POST['password']!=''){
        if(!isset($_SESSION)) 
    { 
        session_start();
        //session_register('username'); 
    } 

        $result = mysqli_query($con, "SELECT * FROM login WHERE username='" . $_POST["username"] . "' and password = '". $_POST["password"]."'");
        while($row  = $result->fetch_assoc($result) ){
        if(is_array($row)) {
            $_SESSION["username"] = $row[$_POST["username"]];
            $_SESSION['username'] = $_POST["username"];

            header("Location:home.php");
            } 
            else {
            $message = "Invalid Username or Password!";

            }

        }
        }

        }

?>

Answer 1

您在代码中混合了面向对象风格和过程风格。只使用一种风格

采用面向对象的风格

$result = $mysqli->query( "SELECT * FROM login WHERE username='" . $_POST["username"] . "' and password = '". $_POST["password"]."'");
 while($row  = $result->fetch_assoc() ){

以程序风格

 $result = mysqli_query($con, "SELECT * FROM login WHERE username='" . $_POST["username"] . "' and password = '". $_POST["password"]."'");
 while($row  = mysqli_fetch_assoc($result) ){

阅读http://php.net/manual/en/mysqli-result.fetch-assoc.php