Esempio rapido:
index.htm
[html]
<form action="show.php" method="post">
<input type="text" name="testo">
<input type="submit" name="ok" value="Invia">
</form>
[/html]show.php
[php]
<?php
$testo = @$_POST["testo"];
?>
<!-- html -->
<input type="text" name="testo" value="<?php echo $testo; ?>">
[/php]Ciao!