<?php

class DbLayer {
	
	private static $instance = null;
	private $db;
	
	private function __construct(){
		$instance = new self();
		$instance->db = new PDO('mysql:host=127.0.0.1;dbname=themoves', ...
		
	}
	
	public static function getInstance(){
		if(is_null(self::$instance)){
			self::$instance = new self();
		}
		return self::$instance->$db;
	}
	
}

?>