Calcolatrice

<?php

print'<form action="">
<input type="text" maxlenght="20" name="n1" value="'.$_GET['n1'].'">
<select name="op">
<option value="1"'; if($_GET['op']== 1){echo"selected";} print'>+</option>
<option value="2"'; if($_GET['op']== 2){echo"selected";} print'>-</option>
<option value="3"'; if($_GET['op']== 3){echo"selected";} print'>x</option>
<option value="4"'; if($_GET['op']== 4){echo"selected";} print'>/</option>
</select>
<input type="text" maxlenght="20" name="n2" value="'.$_GET['n2'].'">
<input type="submit" value="Calcola">
</form><br><br>
Risultato =';
if($_GET['op'] == "1"){ print $_GET['n1']+$_GET['n2']; }
if($_GET['op'] == "2"){ print $_GET['n1']-$_GET['n2']; }
if($_GET['op'] == "3"){ print $_GET['n1']*$_GET['n2']; }
if($_GET['op'] == "4"){ print $_GET['n1']/$_GET['n2']; }
?>