php Class DataHolder protected data array Class composer extends DataH

<?php
Class DataHolder {
	protected $data = array();
}
Class composer extends DataHolder {

	public function __construct (array $resource)
	{
		$this->resource = $resource;
	}

	public function compile ()
	{
		foreach ($this->resource as $r) 
		{
			$r->compile();
		}
	}

	public function write ()
	{
		print_r($this->data);
	}
}
Class data1 extends DataHolder {
	public function compile ()
	{
		$this->data[] = 'a';
	}
}
Class data2 extends DataHolder {
	public function compile ()
	{
		$this->data[] = 'b';
	}
}
Class data3 extends DataHolder {
	public function compile ()
	{
		$this->data[] = 'c';
	}
}

$r = new composer(array(
		new data1,
		new data2,
		new data3
	));
$r->compile();
$r->write();
?>