>>947
計算結果を内部に持っても良いのなら、以下のようなのはどう？

class keisan {
private $result;
function __construct($a) {
$result = $a;
}
function tasizan($b) {
$this->result += $b;
retun $this;
}
function hikizan($b) {
$this->result -= $b;
return $this;
}
function kakezan($b) {
$this->result *= $b;
return $this;
}
function warizan($a,$b) {
$this->result /= $b;
return $this;
}
function kekka {
retun $this->result;
}
}

$obj=new keisan;
$kekka = $obj->tasizan(5)->kakezan(20)->kekka();