Example of generating verification code by php GD library

验证码


请输入验证码

2、生成验证码 auth.php

   session_start();
   header("Content-type:image/png");
   $img_width=100;
   $img_height=20;
   srand(microtime()*100000);
   for($i=0;$i<4;$i++)
   {
        $new_number.=dechex(rand(0,15));
   }
   $_SESSION[check_auth]=$new_number;
   $new_number=imageCreate($img_width,$img_height);//创建图象
   ImageColorAllocate($new_number,255,255,255);  //设置背景色为白色
   for($i=0;$i
   {
       $font=mt_rand(3,5);
       $x=mt_rand(1,8) + $img_width*$i/4;
       $y=mt_rand(1,$img_height/4);
       $color=imageColorAllocate($new_number,mt_rand(0,100),mt_rand(0,150),mt_rand(0,200));//设置字符颜色
       imageString($new_number,$font,$x,$y,$_SESSION[check_auth][$i],$color);//输出字符
   }
   ImagePng($new_number);
   ImageDestroy($new_number);
?>

3、提交页面 check_auth.php

   session_start();
   $auth=$_POST['auth'];
   if(empty($auth))
   {
       echo '错误：验证码不能为空';
       die;
   }
   if($auth==$_SESSION['check_auth'])
   {
       echo '正确';
   }
   else
   {
       echo '错误：验证码输入错误';
   }
?>