Creating images using php

[Cagecrawler]

I'm trying to create an image to use for registration to stop bots.  I've managed to create the image, but when I try to insert anything into the file, or insert it into another file, I get the following error:
[code]
The image “register.php” cannot be displayed, because it contains errors.
[/code]
In this case, the image code is in key.php, and the file I'm trying to insert it into is called register.php.

Can anybody help please?

[Cagecrawler]

Here's key.php:

[code]<?php
function genText($length) {
$p_chars=md5(time()); // can be any set of characters
while(strlen($out_str)< $length)
{
$out_str.= $p_chars{rand()%(strlen($p_chars))};
}
return $out_str;
}

$rand_string = genText(8);
header ("Content-type: image/png");
$im = imagecreate(60, 20);
$bg = imagecolorallocate($im, 0, 255, 255);
$text_color = imagecolorallocate($im, 0, 0, 255);

imagestring($im, 2, 5, 3,$rand_string, $text_color);
imagepng($im);
imagedestroy($im);
?>[/code]

[Cagecrawler]

Solved... I wasn't using <img src="key.php">