<form action='index.php' method='GET'> <label for='a'>a = </a> <input type='text' id='a' name='a' value='0'> <label for='b'>b = </a> <input type='text' id='b' name='b' value='0'> <input type='submit' value='Oblicz'> </form>
$a = (isset($_GET['a']))?$_GET['a']:0; $b = (isset($_GET['b']))?$_GET['b']:0; echo "a = $a<br>"; echo "b = $b<br>"; echo "Suma: " . ($a + $b);