[TYPO3] POST and GET in backend extension

[Lasse Guldsborg]

Hi list

Could someone please help me understand how to handle POST and GET in 
backend extension programming?
Perhaps by correcting this example:

index.php:
<form action="sendmail.html" method="post">
   <input type="hidden" name="username" value="myusername" />
   <input type="submit" value="send" />
</form>

sendmail.html:
<td>Username: <?php echo $_GET["username"]; ?></td>


Cheers,
Lasse