subtraction using PHP

subtraction

#!/usr/bin/php
# Author : Jeffrin
# jeffrin@rocketmail.com
# License GNU GPL V3
# usage : php subtraction.php
<?php
$f='1';
$s='1';
echo  $f - $s ;
echo "n";
?>

output Like

$./subtraction.php
# Author : Jeffrin
# jeffrin@rocketmail.com
# License GNU GPL V3
# usage : php subtraction.php

0
$