發布一個圖形數字驗證代碼

以下代碼本人調試全部通過。運行authpage.php。
<?
/*
* Filename: authpage.php
*/
srand((double)microtime()*1000000);
//驗證用戶輸入是否和驗證碼一致
if(isset($_POST['authinput']))
{
if(strcmp($_POST['authnum'],$_POST['authinput'])==0)
echo "驗證成功！";
else
echo "驗證失敗！";
}
//生成新的四位整數驗證碼
while(($authnum=rand()%10000)<1000);
?>
<form action=authpage.php method=post>
<table>
請輸入驗證碼：<input type=text name=authinput style="width: 80px"><br>
<input type=submit name="驗證" value="提交驗證碼">
<input type=hidden name=authnum value=<? echo $authnum; ?>>
<img src=authimg.php?authnum=<? echo $authnum; ?>>
</table>
</form>
-------------------------------------------------------------------------------------------------------------
<?
/*
* Filename: authimg.php
*/
//生成驗證碼圖片
Header("Content-type: image/PNG");
srand((double)microtime()*1000000);
$im = imagecreate(58,28);
$black = ImageColorAllocate($im, 0,0,0);
$white = ImageColorAllocate($im, 255,255,255);
$gray = ImageColorAllocate($im, 200,200,200);
imagefill($im,68,30,$gray);
//將四位整數驗證碼繪入圖片
imagestring($im, 5, 10, 8, $HTTP_GET_VARS['authnum'], $white);
for($i=0;$i<50;$i++) //加入干擾象素
{
imagesetpixel($im, rand()%70 , rand()%30 , $gray);
}
ImagePNG($im);
ImageDestroy($im);