php 登陆界面数字验证码

<?php
session_start();

// 生成4位随机数字验证码
$code = rand(1000, 9999);

// 将验证码存储在session中
$_SESSION['captcha'] = $code;

// 创建图像
$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, 5, $code, $textColor);

header('Content-type: image/png');
imagepng($image);
imagedestroy($image);
?>

<?php
session_start();

if (isset($_POST['captcha']) && $_POST['captcha'] == $_SESSION['captcha']) {
    echo "验证码正确！";
} else {
    echo "验证码错误！";
}
?>