The s2component function performs registration of a component. The s2component function registers a component using the register method of S2ApplicationContext class.

<?php
require_once('S2Container.php');

class Action {}
s2component('Action');     // same as s2register('Action');

$action = s2get('Action');
var_dump($action);

When specifying a component name, it specifies by the ComponentInfoDef instance which is a return value of the s2component function.

<?php
require_once('S2Container.php');

class Action {}
s2component('Action')->setName('act');

$action = s2get('act');
var_dump($action);