session_start();

// 随机码个数

$_rnd_code = 4;

// 创建随机码

global $_rnum ;

for ($i = 0; $i < 4; $i ++) {

$_rnum .= dechex(mt_rand(0, 15));

}

// 保存到session中

$_SESSION["code"] = $_rnum;

// echo $_rnum;

// 创建图像

$width = 75;

$height = 25;

$_img = imagecreatetruecolor($width, $height);

// 设置背景色

$_white = imagecolorallocate($_img, 255, 255, 255);

imagefill($_img, 0, 0, $_white);

// 设置边框

$_black = imagecolorallocate($_img, 0, 0, 0);

// imagerectangle($_img, 0, 0, $width - 1, $height - 1, $_black);

// 设置随机线条

for ($i = 0; $i < 6; $i ++) {

$_rnd_color = imagecolorallocate($_img, mt_rand(0, 255), mt_rand(0, 255), mt_rand(0, 255));

imageline($_img, mt_rand(0, $width), mt_rand(0, $height), mt_rand(0, $width), mt_rand(0, $height), $_rnd_color);

}

// 设置随机雪花

for ($i = 0; $i < 50; $i ++) {

$_rnd_color = imagecolorallocate($_img, mt_rand(200, 255), mt_rand(200, 255), mt_rand(200, 255));

imagestring($_img, 1, mt_rand(1, $width), mt_rand(1, $height), '#', $_rnd_color);

}

// 输出验证码

for ($i = 0; $i < strlen($_SESSION['code']); $i ++) {

$_rnd_color = imagecolorallocate($_img, mt_rand(0, 100), mt_rand(0, 150), mt_rand(0, 200));

imagestring($_img, 5, $i * $width / $_rnd_code + mt_rand(1, 10), mt_rand(1, $height / 2), $_SESSION['code'][$i], $_rnd_color);

}

// 输出图像

header('Content-Type:image/png');

imagepng($_img);

imagedestroy($_img);

?>

调用: