PHP验证码5

查看效果:php验证码5
<?php
session_start();
$authnum=random(6);
$_SESSION['yan']=$authnum;
Header("Content-type: image/PNG");
$im = imagecreate(55,18);
$red = ImageColorAllocate($im, 153,51,0);
$white = ImageColorAllocate($im, 255,204,0);
$gray = ImageColorAllocate($im, 102,102,0);
imagefill($im,55,18,$red);
for ($i = 0; $i < strlen($authnum); $i++)
{
imagestring($im, 6, 13*$i+4, 1, substr($authnum,$i,1), $white);
}
for($i=0;$i<100;$i++)
{
imagesetpixel($im, rand()%55 , rand()%18 , $gray);
}
ImagePNG($im);
ImageDestroy($im);
function random($length) {
$hash = '';
$chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz';
$max = strlen($chars) - 1;
for($i = 0; $i < $length; $i++) {
$hash .= $chars[mt_rand(0, $max)];
}
return $hash;
}
?>