php登录失败并显示正确的凭据

Question

我有一个项目需要使用php和mySQL为给定场景创建系统。另一个要求是它必须为不同的用户登录。

在我的实现中，即使使用正确的凭据也无法进行身份验证。我正在使用mysqli进行此实现。没有语法错误，字段名称和输入的凭据都是正确的。

有问题的代码（login.php）：

<?php
    session_start(); // Starting Session
    $error=''; // Variable To Store Error Message
    if (isset($_POST['submit'])) {
        if (empty($_POST['username']) || empty($_POST['password'])) {
            $error = "Please enter a username and password";
        } else {
        // Define $username and $password
        $username=$_POST['username'];
        $password=$_POST['password'];
        // Calls the 'connect.php' to connect to the database and select the database
        require 'db/connect.php'; 
        // To protect MySQL injection for Security purpose
        $username = stripslashes($username);
        $password = stripslashes($password);
        $username = mysql_real_escape_string($username);
        $password = mysql_real_escape_string($password);

        // SQL query to fetch information of registerd users and finds user match.
        $result = $db->query("SELECT * FROM `users` WHERE 'usr_pwd'='$password' AND 'usr_name'='$username'");
        if ($result->num_rows == 1) {
            $_SESSION['login_user']=$username; // Initializing Session
            header("location: test.php"); // Redirecting To Other Page
        } else {
            $error = "Username or Password is invalid";
        }
        mysqli_close($db); // Closing Connection
        }
    }
?>

我还将github repo链接到我的代码：https://github.com/gussippi/furniture-store