Indie-Resource.com

I keep getting this error:

Notice: Undefined index: email in C:\wamp\www\orb\launchPage\newsletter.php on line 89

I know I'm missing something simple here but just can't seem to see it.
This is the code from newsletter.php:

<?php


$newsletterFileName = "interested.txt";


function GetField($input) {
$input=strip_tags($input);
$input=str_replace("<","<",$input);
$input=str_replace(">",">",$input);
$input=str_replace("#","%23",$input);
$input=str_replace("'","`",$input);
$input=str_replace(";","%3B",$input);
$input=str_replace("script","",$input);
$input=str_replace("%3c","",$input);
$input=str_replace("%3e","",$input);
$input=trim($input);
return $input;
}



/**Validate an email address.
Provide email address (raw input)
Returns true if the email address has the email
address format and the domain exists.
*/
function validEmail($email)
{
$isValid = true;
$atIndex = strrpos($email, "@");
if (is_bool($atIndex) && !$atIndex)
{
$isValid = false;
}
else
{
$domain = substr($email, $atIndex+1);
$local = substr($email, 0, $atIndex);
$localLen = strlen($local);
$domainLen = strlen($domain);
if ($localLen < 1 || $localLen > 64)
{
// local part length exceeded
$isValid = false;
}
else if ($domainLen < 1 || $domainLen > 255)
{
// domain part length exceeded
$isValid = false;
}
else if ($local[0] == '.' || $local[$localLen-1] == '.')
{
// local part starts or ends with '.'
$isValid = false;
}
else if (preg_match('/\\.\\./', $local))
{
// local part has two consecutive dots
$isValid = false;
}
else if (!preg_match('/^[A-Za-z0-9\\-\\.]+$/', $domain))
{
// character not valid in domain part
$isValid = false;
}
else if (preg_match('/\\.\\./', $domain))
{
// domain part has two consecutive dots
$isValid = false;
}
else if
(!preg_match('/^(\\\\.|[A-Za-z0-9!#%&`_=\\/$\'*+?^{}|~.-])+$/',
str_replace("\\\\","",$local)))
{
// character not valid in local part unless
// local part is quoted
if (!preg_match('/^"(\\\\"|[^"])+"$/',
str_replace("\\\\","",$local)))
{
$isValid = false;
}
}
}
return $isValid;
}


$email = GetField($_GET['email']);
$pass = validEmail($email);

if ($pass) {
$f = fopen($newsletterFileName, 'a+');
$read = fread($f,filesize($newsletterFileName));
If (strstr($read,"@")) {
$delimiter = ";";
}
if (strstr($read,$email)) {
echo 3;
} else {
fwrite($f, $delimiter . $email);
echo 1;
}
fclose($f);
} else {
echo 2;
}
?>

Line 89 is this one:

$email = GetField($_GET['email']);

Thanks in advance for any help.

check your url is email even defined? as this shows it is not...

AAAHHHHHH Thanks Halls! I knew it was going to be something simple I just wasn't seeing.