class TController {

	private $components = new array();

	public function register(&$comp) { $components[] = $comp; }

	public function getHeader() {
		foreach ($components as $comp) {
			$comp->getHeader();
		}
	}

}

interface Component {

	public function getHeader()

}

class DropDown implements Component {

	public function getHeader() {
		include('ddHeader.php');
	}

}

$controller = new TController();
$dd = new DropDown();
$controller->register($dd);

<html>
<head>
$controller->getHeader();
</head>
...