Why doesn't this work?
Code:
<?php
    if ($_POST['textbox1'] != "")
		$_ENV['mytestzeststring'] = $_POST['textbox1'];
	print $_ENV['mytestzeststring'];
?>

<form name="registerform" id="registerform" action="<?php echo site_url('wp-login.php?action=register', 'login_post') ?>" method="post">
	  <input type="text" name="testbox1"/>
	  <input type="submit" value="Click me!"/>

</form>
Wouldn't this present on the page before the form declaration whatever the user types in the test box?