dedecms后台验证码

<?php
// 生成验证码
function generateCaptcha() {
    $length = 4;
    $chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
    $captcha = '';
    for ($i = 0; $i < $length; $i++) {
        $captcha .= $chars[rand(0, strlen($chars) - 1)];
    }
    $_SESSION['captcha'] = $captcha;
    $image = imagecreatetruecolor(100, 30);
    $bgColor = imagecolorallocate($image, 255, 255, 255);
    imagefill($image, 0, 0, $bgColor);
    $textColor = imagecolorallocate($image, 0, 0, 0);
    imagestring($image, 5, 20, 5, $captcha, $textColor);
    header('Content-type: image/png');
    imagepng($image);
    imagedestroy($image);
}

// 验证验证码
function verifyCaptcha($input) {
    if (isset($_SESSION['captcha']) && $_SESSION['captcha'] === $input) {
        return true;
    }
    return false;
}
?>