session_start();

function myf($l){

if(!ereg("^[0-9]+$",$l) || $l>1000) return;

for($c='123456789ABCDEFGHIJKLMNPQRSTUVWXYZ',$r='';$l>0;$l--,$r.=$c[rand(0,61)]);

return $r;

}

$authnum=myf(6);

session_register("auth");

$auth=$authnum;





//生成验证码图片

Header("Content-type: image/PNG");

$im =@imagecreate($wid=11*strlen($authnum),20);

imagefill($im,68,30,ImageColor($im,'#f7f7f7'));



//将四位整数验证码绘入图片

//位置交错

for ($i = 0; $i < strlen($authnum); $i++)

{

$i%2 == 0?$top = 1top = 4;

imagestring($im, 5, 10*$i+6, $top, substr($authnum,$i,1),ImageColor($im,'#FF0000'));

}



for($i=0;$i<150;$i++) //加入干扰象素

{

imagesetpixel($im, rand()%90 , rand()%30 , ImageColor($im,'#FF7700'));

}



ImagePNG($im);

ImageDestroy($im);

function ImageColor($im,$color)

{

preg_match_all("/([0-f]){2,2}/i",$color,$out);

if(count($out[0])!=3)$out[0]=array_pad ($out[0],3,0);

return ImageColorAllocate($im, hexdec($out[0][0]),hexdec($out[0][1]),hexdec($out[0][2]));

}

&lt;? session_start();?&gt;

&lt;? header("content-type:text/html;charset=gb2312");?&gt;

<form action="test01.php" method="post">

<input type=text name=number>

<img src=checkNumber.php>&lt;? session_unset();?&gt;

<input type="submit" name="Submit" value="提交" />

</form>

session_start();

header("content-type:text/html;charset=gb2312");

$se=$_SESSION['auth'];

$number=$_POST['number'];

if($number != $se || empty($number))

{

print("校验码不正确!");

die();

}

else{

print("确!");

die();

}