还算功能比较全的PHP验证码类

看到PHP100视频34讲写的php验证码类，支持自定义图片大小、字符个数、字符类型、字符大小、图片类型、汉字验证码、干扰线等，注释详细

字体文件是微软雅黑，和验证码文件同目录，文件名msyh.ttf，可以从C:\windows\fonts目录找到，复制到同目录即可

/**

 * @version        Id:  imgcode.php 2012-11-30   k

 * @package        imgcode.php

 * @Purview           default

 * @link           http://www.3oom.com

 */

    $img = new img_code();

    $img->show();

class img_code{

    private $img_type = &＃39;png&＃39;;//输出图片类型 png,gif,jpg

    private $line      = TRUE;//是否增加干扰线

    private $text      = &＃39;2&＃39;;//验证码类型：0数字，1字母，2汉字

    private $text_size= 20;//字体大小

    private $length      = 4;//字符串长度

    private $width      = 120;//图片宽度，像素

    private $height      = 40;//图片高度，像素

    private $font_file= &＃39;msyh.ttf&＃39;;//字体文件

    public  $img      = &＃39;&＃39;;

    /*

    * 创建图片

    */

    private function img_create(){

        $this->img = imagecreate($this->width, $this->height);

        imagecolorallocate($this->img, 255,255,255);

    }

    /*

    * 显示图片

    */

    public function show(){

        @session_start();

        $this->img_create();

        if($this->line){

        $this->img_line();

        }

        $this->img_text();

        $this->img_header();

        imagedestroy($im);

        exit();

    }

    /*

    * 生成字符串

    */

    private function img_text(){

        $rand_string = &＃39;&＃39;;

        $im = &$this->img;

        $fontColor[]  = imagecolorallocate($im, 0x15, 0x15, 0x15);

        $fontColor[]  = imagecolorallocate($im, 0x95, 0x1e, 0x04);

        $fontColor[]  = imagecolorallocate($im, 0x93, 0x14, 0xa9);

        $fontColor[]  = imagecolorallocate($im, 0x12, 0x81, 0x0a);

        $fontColor[]  = imagecolorallocate($im, 0x06, 0x3a, 0xd5);

        if($this->text<2){

            //数字，字母

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

                if($this->text){

                    $c=chr(mt_rand(65,90));

                }else{

                    $c=chr(mt_rand(48,57));

                }

                if( $c==&＃39;I&＃39; ) $c = &＃39;K&＃39;;

                if( $c==&＃39;O&＃39; ) $c = &＃39;E&＃39;;

                $rand_string[]=$c;

            }   

        }else{

            //汉字,此处可以引入汉字文件

           $arr=array(&＃39;大&＃39;,&＃39;小&＃39;,&＃39;多&＃39;,&＃39;少&＃39;,&＃39;人&＃39;,&＃39;天&＃39;,&＃39;水&＃39;,&＃39;土&＃39;,&＃39;木&＃39;,&＃39;火&＃39;,&＃39;云&＃39;);

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

                $l = count($arr)-1;               

                //文件编码为gbk需要转换

                //$rand_string[] = iconv(&＃39;gb2312&＃39;,&＃39;utf-8&＃39;,$arr[mt_rand(0,$l)]);

                $rand_string[] = $arr[mt_rand(0,$l)];

            }

        }

          $_SESSION[&＃39;imgcode&＃39;]=$rand_string;

          $_c = count($rand_string);

          for($i=0;$i<$_c;$i++)

        {

            if($this->text == 1){

            $rand_string[$i] = strtoupper($rand_string[$i]);

            }

            $c_fOntColor= $fontColor[mt_rand(0,4)];

            $y = $this->height-($this->height-$this->text_size)/2;

            $x = ($this->width-($this->text_size+2)*$this->length)/2;

            $y_pos = $i==0 ? $x : $i*($this->text_size+2)+$x;

            $c = mt_rand(0, 15);

            @imagettftext($im, $this->text_size, $c, $y_pos, $y, $c_fontColor, $this->font_file, $rand_string[$i]);

        }

    }

    /*

    * 生成线条

    */

    private function img_line(){

        $im = &$this->img;

        $img_width = $this->width;

        $img_height= $this->height;

            //背景横线

        $lineColor1 = imagecolorallocate($im, 0xda, 0xd9, 0xd1);

        for($j=3; $j<=$img_height-3; $j=$j+3)

        {

            imageline($im, 2, $j, $img_width - 2, $j, $lineColor1);

        }

        //背景竖线

        $lineColor2 = imagecolorallocate($im, 0xda,0xd9,0xd1);

        for($j=2;$j<$img_width-6;$j=$j+6)

        {

            imageline($im, $j, 0, $j+8, $img_height, $lineColor2);

        }

        //画边框

        if( $use_boder && $filter_type == 0 )

        {

            $bordercolor = imagecolorallocate($im, 0x9d, 0x9e, 0x96);

            imagerectangle($im, 0, 0, $img_width-1, $img_height-1, $bordercolor);

        }

    }

    /*

    * 生成输出

    */

    private function img_header(){

        header("Pragma:no-cache\r\n");

           header("Cache-Control:no-cache\r\n");

            header("Expires:0\r\n");

        if($this->img_type == &＃39;jpg&＃39;){

            header(&＃39;Content-type: image/jpeg&＃39;);

            imagejpeg($this->img);

        }else if($this->img_type == &＃39;png&＃39;){

            header(&＃39;Content-type: image/png&＃39;);

            imagepng($this->img);

        }else{

            header(&＃39;Content-type: image/gif&＃39;);

            imagegif($this->img);

        }

    }

}

 文章来源：http://www.3oom.com/blog/50.html