php实现动态验证码

<?php
session_start();

// 生成随机验证码
$code = substr(md5(uniqid(rand(), true)), 0, 6);
$_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, $bgColor);
imagettftext($image, 20, 0, 10, 20, $textColor, 'arial.ttf', $code);

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";
}
?>