<?php

class db
{
   protected $db = null;
   public function __construct($db_type,$db_host,$db_user,$db_pass, $db_name) {
      $this->db = new {$db_type}($db_host, $db_user, $db_pass, $db_name);
   }
}

class MYSQL extends database implements idb
{

   public function connect() {
     mysql_connect($this->db_host, $this->db_user, $this->db_pass);
     mysql_select_db($this->db_name);
   }

   public function fetch_assoc() {
     return mysql_fetch_assoc($this->db_link);
   }

   public function query($sql) {
     mysql_query($sql, $this->db_link);
   }
}

abstract class database
{
   protected $db_host = null;
   protected $db_user = null;
   protected $db_pass = null;
   protected $db_name = null;

   protected $db_link = null;

   public function __construct($db_host, $db_user, $db_pass, $db_name) {
     $this->db_host = $db_host;
     $this->db_user = $db_user;
     $this->db_pass = $db_pass;
     $this->db_name = $db_name;

     $this->connect();
   }
}

interface idb
{
  public function connect();
  public function fetch_assoc();
  public function query($sql);
}

// Usage
$db = new db('MYSQL', 'localhost', 'root', '', 'localhost');
$db->query('SELECT * FROM table');
$result = $db->fetch_assoc();