<?php class calculator { public $a; public $b; public $c; public $d; public $y; public $z; function plus($a, $b, $c, $d) { $y = $a + $b; $z = $c + $d; echo $z; } function minus($a, $b) { $y = $a + $b; $z = $c + $d; echo $z; } } $obj = new calculator(); $obj->plus(1, 2, 3, 4); $obj->minus(9, 8, 7, 6);