注册和登录时的验证码

绘制验证码：此代码是放在CI框架libraries里边的。

<?php  
  
    class Captcha_code     
    {  
        var $width='60';  
        var $num='4';  
        var $height='20';  
        var $name='randcode';  
              
        function show()  
        {  
            Header("Content-type: image/gif");  
            /*  
            * 初始化  
            */  
            $border = 0; //是否要边框 1要:0不要  
            $how = $this->num; //验证码位数  
            $w = $this->width; //图片宽度  
            $h = $this->height; //图片高度  
            $fontsize = 5; //字体大小  
            $alpha = "abcdefghijkmnopqrstuvwxyz"; //验证码内容1:字母  
            $number = "023456789"; //验证码内容2:数字  
            $randcode = ""; //验证码字符串初始化  
            srand((double)microtime()*1000000); //初始化随机数种子  
              
            $im = ImageCreate($w, $h); //创建验证图片  
              
            /*  
            * 绘制基本框架  
            */  
            $bgcolor = ImageColorAllocate($im, 255, 255, 255); //设置背景颜色  
            ImageFill($im, 0, 0, $bgcolor); //填充背景色  
            if($border)  
            {  
                $black = ImageColorAllocate($im, 0, 0, 0); //设置边框颜色  
                ImageRectangle($im, 0, 0, $w-1, $h-1, $black);//绘制边框  
            }  
              
            /*  
            * 逐位产生随机字符  
            */  
            for($i=0; $i<$how; $i++)  
            {     
                $alpha_or_number = mt_rand(0, 1); //字母还是数字  
                $str = $alpha_or_number ? $alpha : $number;  
                $which = mt_rand(0, strlen($str)-1); //取哪个字符  
                $code = substr($str, $which, 1); //取字符  
                $j = !$i ? 4 : $j+15; //绘字符位置  
                $color3 = ImageColorAllocate($im, mt_rand(0,100), mt_rand(0,100), mt_rand(0,100)); //字符随即颜色  
                ImageChar($im, $fontsize, $j, 3, $code, $color3); //绘字符  
                $randcode .= $code; //逐位加入验证码字符串  
            }  
              
            /*  
            * 添加干扰  
            */  
            for($i=0; $i<5; $i++)//绘背景干扰线  
            {     
                $color1 = ImageColorAllocate($im, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255)); //干扰线颜色  
                ImageArc($im, mt_rand(-5,$w), mt_rand(-5,$h), mt_rand(20,300), mt_rand(20,200), 55, 44, $color1); //干扰线  
            }     
            for($i=0; $i<$how*15; $i++)//绘背景干扰点  
            {     
                $color2 = ImageColorAllocate($im, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255)); //干扰点颜色   
                ImageSetPixel($im, mt_rand(0,$w), mt_rand(0,$h), $color2); //干扰点  
            }  
              
            //把验证码字符串写入session 
            $CI = &get_instance();            

            $CI->load->library('session');

            $randcode = md5($randcode);
              
            $CI->session->set_userdata('code',$randcode);  
                           
            /*绘图结束*/  
            Imagegif($im);  
            ImageDestroy($im);  
            /*绘图结束*/  
        }  
    }  
?>  

view文件代码

验证码：<input id="verify_text" name="verify_text" type="text">
          <img src="http://gameapi.xiaoyou-game.com/user/verify_image"   id="verify_code">    
看不清？<a href="javascript:changeCode();">换一张</a>     

js代码

<script type="text/javascript">
    function changeCode(){
        $("#verify_code").attr("src","http://gameapi.xiaoyou-game.com/user/verify_image?r="+Math.random());      
    }
</script>

controller代码

 public function verify_image() 
    {               
        $this->load->library('captcha_code');
        ob_clean(); 
        $this->captcha_code->show();   
    } 

 $verify_text = md5($post['verify_text']);
 $verify_code = $this->session->userdata('code'); 
//两相比较即可，若相同，则验证码成功