Best way to include file in PHP?

I'm currently developping a PHP web application and I would like to know what is the best manner to include files (include_once) in a way where the code it is still maintanable. By maintanable I mean that if I want to move a file, It'd be easy to refactor my application to make it work properly.

I have a lot of files since I try to have good OOP practices (one class = one file).

Here's a typical class structure for my application:

namespace Controls
{
use Drawing\Color;

include_once '/../Control.php';

class GridView extends Control
{
    public $evenRowColor;

    public $oddRowColor;

    public function __construct()
    {
    }

    public function draw()
    {
    }

    protected function generateStyle()
    {
    }

    private function drawColumns()
    {
    }
}
}