php 模拟登录带验证码

<?php
session_start();

// 生成验证码
if (empty($_SESSION['captcha'])) {
    $_SESSION['captcha'] = substr(md5(uniqid(mt_rand(), true)), 0, 5);
}

// 验证码图片
header('Content-type: image/png');
$image = imagecreatetruecolor(100, 30);
$bgColor = imagecolorallocate($image, 255, 255, 255);
$textColor = imagecolorallocate($image, 0, 0, 0);
imagefilledrectangle($image, 0, 0, 100, 30, $bgColor);
imagestring($image, 5, 20, 8, $_SESSION['captcha'], $textColor);
imagepng($image);
imagedestroy($image);

// 处理登录请求
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    if (isset($_POST['username']) && isset($_POST['password']) && isset($_POST['captcha'])) {
        $username = $_POST['username'];
        $password = $_POST['password'];
        $userCaptcha = $_POST['captcha'];

        // 验证验证码
        if (strtolower($userC奘aptcha) === strtolower($_SESSION['captcha'])) {
            // 验证用户名和密码
            if ($username === 'admin' && $password === '123456') {
                echo "登录成功！";
            } else {
                echo "用户名或密码错误！";
            }
        } else {
            echo "验证码错误！";
        }
    }
}
?>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>模拟登录</title>
</head>
<body>
    <form method="post">
        用户名：<input type="text" name="username"><br>
        密码：<input type="password" name="password"><br>
        验证码：<input type="text" name="captcha">
        <img src="login.php" alt="验证码"><br>
        <input type="submit" value="登录">
    </form>
</body>
</html>