如果用户未登录，请阻止打开任何页面

我的web应用程序由2个页面组成（登录页面、主页）

如果用户以前没有登录，我想阻止用户查看主页，所以我做了以下操作：

在主页中，我检查登录身份验证中设置的用户名会话

  session_start();
    if (!isset($_SESSION['LOGIN_STATUS'])||$_SESSION['LOGIN_STATUS']!=true) {
        header('Location:login.php?lang=en');
        exit();
    }

现在：当我打开主页时，我重定向到登录屏幕，这是正确的，但当我登录然后注销，然后尝试再次登录时，我也重定向到登录页面，无法再次登录

注销时：

session_start();
    unset($_SESSION['username']);
    $lang=$_SESSION['lang'];
    unset($_SESSION['lang']);
    session_unset();
    if(session_destroy()){
        header("Location: login.php?lang=$lang");
        exit;
}

java脚本登录代码：

$(function () {
    var form = $('#main form'),
            arrow = $('#main .arrow');
    $('#main .row input').val('');
    function submitLogin(enteredUsername, enteredPassword) {
        $.ajax({
            url: './webService/CheckLogin.php',
            type: 'post',
            data: {username: enteredUsername, password: enteredPassword},
            cache: false,
            success: function (resp) {
                if (resp.toString() === "true") {
                    window.location = 'Main.php';
                } else {
                    // fail code here.
                    alert("Login Failed");
                }
            }
        });
    }
    // Handle form submissions
    form.on('submit', function (e) {
        var user = document.getElementById("username").value;
        var pass = document.getElementById("password").value;
        submitLogin(user, pass);
    });
});

检查Login.php

 require("./DbConnection.php");
    session_start();
    if(isset($_POST['username']) && !empty($_POST['username'])){
        $username = ($_POST['username']);
    }
    if(isset($_POST['password']) && !empty($_POST['password'])){
        $password = ($_POST['password']);
    }
    AuthenticateUser($username, $password);
    function AuthenticateUser($username, $password) {
        $conn = OpenConnection();
        $tsql = "select userName,Password from Users ";
        $stmt = sqlsrv_query($conn, $tsql);
        if ($stmt === false) {
            echo "Error in executing query.</br>";
            die(print_r(sqlsrv_errors(), true));
        }
        while ($row = sqlsrv_fetch_array($stmt)) {
            if ($username == $row[0] && $password == $row[1]) {
                $res = 'true';
                $_SESSION['LOGIN_STATUS']=true;
                $_SESSION['username'] = $username;
                $_SESSION['password'] = $password;
                break;
            } else {
                $res = 'FALSE';      
            }
        }
        CloseConnection($stmt, $conn);
        echo $res;
    }