<?php
        function login() {
            //用户名为空判断
            if (empty($_POST['username'])) {
                $GLOBALS['message'] = '请填写用户名';
                return;
            }
            //密码为空判断
            if (empty($_POST['password'])) {
                $GLOBALS['message'] = '请填写密码';
                return;
            }
            $username = $_POST['username'];
            $password = $_POST['password'];
            $conn = mysqli_connect(DB_HOST, DB_USER, DB_PASS, DB_NAME);
            if (!$conn) {
                echo '数据库连接失败,出错原因是'.mysqli_connect_error();
            }
            //登录查询
            $login_result = mysqli_query($conn, "select * from ft_user WHERE username='{$username}' and password '{$password}';");
            //如果通过输入的 username和password查询结果行数大于0，登录成功,否则提示用户名密码错误
            if ($login_result->num_rows > 0) {
                header('Location: ./index.php');
            } else {
                $GLOBALS['message'] = '用户名或密码错误';
            }
        }
        //判断是否post提交
        if ($_SERVER['REQUEST_METHOD'] == 'POST') {
            login();
        }
        ?>