o così...a me piace di +
codice:
<html>
<head>
<title>Programma php</title>	 
</head>
 
<body>
<? 
if ($_POST['mostra']==1)
{
  $file=file("testoscritto.txt");
  $max=count($file);
  for ($i=0; $i<=$max; $i++)
    echo 'Riga '.$i.': '.$file[$i];
}
else 
{
?>
  <form method="POST">
  <input type="hidden" value="1" name="mostra">
  <input type="submit">
  </form>		 
<?
}
?>
</body>
</html>