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);