Best way to integrate classes

From: Swartz (swartz_at_inbox.ru)
Date: 03/06/04 

Date: Sat, 6 Mar 2004 15:52:41 -0600

Hi all.

I'm working here on a small project of mine. I'm not new to programming, but
I'm new to PHP. You have to understand that I'm coming from C++, OOP world,
so my code might seems a little too "object"-ified.

Anyways, I've created a wrapper class for MySQL connectivity. It's barebones
for now, no error checking or anything. So now I'm trying to create
user/session-handling class that would work with the data stored in the
database via DB class.

What is the best approach to integrate the two classes? How would you do it?

I see three possible solutions:

1.) Have the Session class extend the DB class?
class Session extends DB {
    // login();
    // logout();
    // etc...
}

This doesn't really make sense to me in terms of logical iheritance. Session
is not really a DB-handling class. Besides, I'm unclear on a few things
here. Will the constructor for DB class be called automatically and create a
connection (it should in my mind) or should I be re-initializing all
inherited vars?

2.) First, instantiate an object of DB:
$oDB = new DB();

Then use it via global declaration in Session class

class Session {
    global $oDB;

    // login();
    // logout();
    // etc...
}

Not the prettiest way, but it works. It would also allow to reuse the same
MySQL connection via $oDB object further in the code.

3.) Instantiate DB object as part of Session's vars:

class Session {
    $_oDB = new DB();

    // login();
    // logout();
    // etc...
}

The only drawback I can see is that I would be unable to reuse the MySQL
connection outside of Session class. I'd have to create a totaly new DB
object.

Oh and here's the DB class.

// +++++++++++++++++++ DB CLASS +++++++++++++++++
class DB {

 // public variables
 var $sServer;
 var $sPort;
 var $sUser;
 var $sPass;
 var $sDatabase;

 // private variables
 var $_link_id;
 var $_result_id;
 var $_last_query;

 // Constructor, uses db_connect()
 function DB ($user, $pass, $database, $server='localhost', $port='3306') {
  $this->connect($user, $pass, $database, $server, $port);
 }

 // Opens a connection to a db-server and selects a db
 function connect ($user, $pass, $database, $servet, $port) {
  $this->sServer = $server;
  $this->sPort = $port;
  $this->sUser = $user;
  $this->sPass = $pass;
  $this->sDatabase = $database;

  $this->_link_id = mysql_connect("$server:$port", $user, $pass);

  $this->select_db($database, $this->_link_id);
 }

 // Closes connection to the database
 function disconnect () {
  $this->free_result();
  mysql_close($this->_link_id);
  unset ($this->_link_id, $this->_result_id);
 }

 // Changes database in use
 function select_db ($database) {
  mysql_select_db($this->sDatabase, $this->_link_id);
 }

 // Run db query
 function query ($query) {
  $this->_last_query = $query;
  $this->_result_id = mysql_query($query, $this->_link_id);
 }

 // Frees up the memory required to store last query's results
function free_result () {
  mysql_free_result($this->_result_id);
  unset ($this->_result_id);
 }

 // Returns a single record array from the query results
 function fetch_row () {
  return mysql_fetch_row($this->_result_id);
 }

 // Returns a single record as associative array from query results
 function fetch_assoc () {
  return mysql_fetch_assoc($this->_result_id);
 }

 // Returns a single record as object from query results
 function fetch_object () {
  return mysql_fetch_object($this->_result_id);
 }

 // Returns number of records found after SELECT statement
 function num_rows () {
  return mysql_num_rows($this->_result_id);
 }

 // Return number of rows affected from INSERT, UPDATE, DELETE statements
 function affected_rows () {
  return mysql_affected_rows($this->_link_id);
 }

 // Returns current db link_id
 function get_link_id () {
  return $this->_link_id;
 }

 // Return current db result_id
 function get_result_id () {
  return $this->_result_id;
 }

 // Return last query ran
 function get_last_query () {
  return $this->_last_query;
 }
 // -----------------------------------------------------------------------
}

Any comments are welcome, perhaps there're other way to do this that I'm not
seeing. 

--
Swartz

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