PHP 生成图像验证码，个性化参数

<?php
// 产生一个随机字符串
function buildRandomString($type = 1, $length = 4) {
if ($type == 1) {
$chars = join("", range(0, 9));
} elseif ($type == 2) {
// array_merge 把两个数组合并为一个数组：
$chars = join("", array_merge(range("A", "Z"), range("A", "Z")));
} elseif ($type == 3) {
$chars = join("", array_merge(range("A", "Z"), range(0, 9)));
} elseif ($type == 4) {
$chars = join("", array_merge(range("a", "z"), range("A", "Z"), range(0, 9)));
}

if ($length > strlen($chars)) {
exit("字符串长度不够");
}

// 随机地打乱字符串中的所有字符：
$chars = str_shuffle($chars);

// 截取字符串
return substr($chars, 0, $length);
}

// 使用GD库做验证码
function verifyImage($type = 1, $length = 4, $pixel = 1, $line = 0) {
// session_start();

$width  = 100; // 画布宽
$height = 40; // 画布高
$image  = imagecreatetruecolor($width, $height); // 创建验证码画布

$black        = imagecolorallocate($image, 0x00, 0x00, 0x00);
$green        = imagecolorallocate($image, 0x00, 0xFF, 0x00);
$blue         = imagecolorallocate($image, 0x00, 0x00, 0xFF);
$white        = imagecolorallocate($image, 0xFF, 0xFF, 0xFF);
$random_color = imagecolorallocate($image, mt_rand(0, 200), mt_rand(0, 200), mt_rand(0, 200)); // 随机颜色
$fontfiles    = array("FZSTK.TTF", "msyh.ttc", "msyhbd.ttc", "msyhl.ttc", "simsun.ttc", "SIMYOU.TTF", "STXINGKA.TTF"); // 随机字体

// 矩形区域着色
imagefill($image, 0, 0, $white);
// imagefilledrectangle($image, 0, 0, $width, $height, $white);

// 产生一个随机字符串
// $type   = 1; // 验证码类型
// $length = 4; // 验证码长度
$chars  = buildRandomString($type, $length);

// 保存字符串，以待验证
$sess_name            = "verify";
$_SESSION[$sess_name] = $chars;

// 将字符串写到图片中
for ($i = 0; $i < $length; $i ++) {
$size     = mt_rand(20, 25); // 字符字号大小
$angle    = mt_rand(- 15, 15); // 旋转角度
$x        = 5 + $i * $size; // x y 两参数为文字的坐标值 (原点为左上角)
$y        = mt_rand(28, 38);
$color    = $random_color;
$fontfile = "../fonts/" . $fontfiles[mt_rand(0, count($fontfiles) - 1)];
$text     = substr($chars, $i, 1);
imagettftext($image, $size, $angle, $x, $y, $color, $fontfile, $text); // 写 TTF 文字到图中。
}

// 加入噪点干扰（可选）
// $pixel = true;
if ($pixel) {
for($i = 0; $i < 30; $i ++) {
imagesetpixel($image, mt_rand(0, $width), mt_rand(0, $height), $black);
imagesetpixel($image, mt_rand(0, $width), mt_rand(0, $height), $green);
imagesetpixel($image, mt_rand(0, $width), mt_rand(0, $height), $blue);
}
}

// 加入直线干扰（可选）
// $line = false;
if ($line) {
for($i = 0; $i < 1; $i ++) {
imageline($image, mt_rand(0, $width), mt_rand(0, $height), mt_rand(0, $width), mt_rand(0, $height), $black);
imageline($image, mt_rand(0, $width), mt_rand(0, $height), mt_rand(0, $width), mt_rand(0, $height), $green);
imageline($image, mt_rand(0, $width), mt_rand(0, $height), mt_rand(0, $width), mt_rand(0, $height), $blue);
}
}

// 输出验证码
ob_clean();
header("content-type: image/png");
imagepng($image);
imagedestroy($image);
}

verifyImage(1, 4, 1, 0);