in.php

<h1>Hello App</h1>
<?php
if(isset($_POST["name"])) {
	?>
	<p>Hello <?php echo htmlspecialchars($_POST["name"]) ?>!</p>
	<p><a href="<?php echo $_SERVER["PHP_SELF"] ?>">try again?</a></p>
	<?php
} else {
	?>
	<p>What's your name?</p>
	<form method="POST">
		<input name="name">
		<input type="submit" value="go">
	</form>
	<?php
}
?>

out.php

<?php if(!isset($_)) $_ = array();
echo '<h1>Hello App</h1>
';
array_push($_, $_POST);
$issetA = array_pop($_);
array_push($_,'name');
array_push($_, isset($issetA[array_pop($_)]));
if(array_pop($_)) {
echo '	<p>Hello ';
array_push($_, $_POST);
array_push($_,'name');
$T = array_pop($_);
$U = array_pop($_);
array_push($_, $U[$T]);
array_push($_, call_user_func_array('htmlspecialchars', array_reverse(array(array_pop($_)))));
echo array_pop($_);
echo '!</p>
	<p><a href="';
array_push($_, $_SERVER);
array_push($_,'PHP_SELF');
$T = array_pop($_);
$U = array_pop($_);
array_push($_, $U[$T]);
echo array_pop($_);
echo '">try again?</a></p>
	';
} else {
echo '	<p>What\'s your name?</p>
	<form method="POST">
		<input name="name">
		<input type="submit" value="go">
	</form>
	';
}