What if I statically call the other class function?

index.php:
include ('dal.php');
include ('html.php');
class main_class {

public $database = new DAL;
public $html = new HTML;

}

dal.php:
class DAL {

function method() {
# Code

}
}

html.php:
class HTML {

function method() {
# Code
DAL::method();
# Code

}
}

Does this code work???