<?php

class ChainMe {

    public function hello() {
        echo 'Hello ';

        return $this;
    }

    public function good($is = false) {
        if ($is === true) {
            echo 'beautiful ';
        }

        return $this;
    }

    public function day() {
        echo "world!\n\n";

        return $this;
    }

}

$happy = new ChainMe();
$happy
    ->hello()
    ->good(true)
    ->day();

$meh = new ChainMe();
$meh->hello()->good()->day();

?>

Hello beautiful world!

Hello world!