<?php

require_once 'string.func.php';

//通过GD库左验证码

//创建画布

$width = 80;

$height = 28;

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

$white = imagecolorallocate($image, 255, 255, 255);

$black = imagecolorallocate($image, 0, 0, 0);

//用填充矩形填充画布

imagefilledrectangle($image, 1, 1, $width-2, $height-2, $white);

$type = 1;

$length = 4;

$chars = buildRandomString($type,$length);

$sess_name = "verify";

$_SESSION[$sess_name] = $chars;

$fontfile = array("msyh.ttf","msyhbd.ttf","simkai.ttf","simsun.ttc","SIMYOU.TTF");

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

    $size = mt_rand(14, 18);

    $angle = mt_rand(-15, 15);

    $x = 5+$i*$size;

    $y = mt_rand(20, 26);

    $fontfile = "../fonts/".$fontfile[mt_rand(0, count($fontfile)-1)];

    $color = imagecolorallocate($image, mt_rand(50,90), mt_rand(80,200), mt_rand(90, 180));

    $text = substr($chars, $i, 1);

    imagettftext ( $image, $size, $angle, $x, $y, $color, $fontfile, $text );

}

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

    imagesetpixel($image, mt_rand(0, $width-1), mt_rand(0, $height-1), $black);

}

header("content-type:image/gif");

imagegif($image);

imagedestroy($image);

以上是代码，运行的时候出现（如图）：