Object-Oriented question

[HiImFreddy]

Hi guys, while the basics of OO programming is pretty easy to understand, I'm still having some problems with some fairly fundamental issues...

I'm trying to create a new object that will allow for basic mysql functions to be more easily used in children of this class. I'm not sure though how the children would access a spefic object and not just the general class.

Here's a simple example of what I'm trying:

class mysqlObject {

  var $last_query;
  var $db_host;

  function mysqlObject($username, $password, $host, $db) {

$this->$db_host = mysql_connect($host, $username, $password);
if (!$this->$db_host) return false;
mysql_select_db($db);

  }

}


class mysqlTable extends mysqlObject  {

  var $last_query;
  var $dbtable;
  function mysqlTable($table)	{

$this->$dbtable = $table;
return $this->$dbtable;

  }

  function select_all() {
    $this->$last_query = "SELECT * FROM $this->dbtable";
    return $this->$last_query;

  }

}

class phpBasic extends mysqlTable  {

  var $db_table;
  function php_basic() {

return true;

  }

  function get_total()  {

$result = mysqlTable::run_query(select_all());
$number = MYSQL_NUMROWS($result);
return $number;

  }


}

$mysql = new mysqlObject('user', 'pass', 'host.com', 'db');
if (!$mysql) $failure = "Cannot connect to database<br>";

$dbtable = new mysqlTable('table');
if (!$dbtable) $failure = "No table of this name<br>";

$basic = new phpBasic();
if (!$basic) $failure = "Something bad happened<br>";

I know this definately will not work but I can't really explain why...

If anyone could just lead me in the right direction at the absolute least, it would be greatly helpful. Please let me know. 🙂 Thanks!

[tbach2]

your code has a syntax error:
$this->$db_host should be $this->db_host and so on.

FWIW,

A good place to look for some sample code would be phplib.

For example, from their code, they use a local.inc to extend the basic library code, eg.

class DB_Example extends DB_Sql {
  var $Host     = "localhost";
  var $Database = "example_database";
  var $User     = "example_user";
  var $Password = "";
}

all that's happening here is to actually set some of the variables so that you don't have to pass them when you instantiate the object. IOW, when I type $db = new DB_Example; I am automatically connected, where if I typed $db = new DB_Sql, I would have to access some method to input host, database, etc.

Another way extending a class can be used is to change the way one of the methods works:

class Example_Challenge_Auth extends Auth {
  var $classname      = "Example_Challenge_Auth";

  var $lifetime       =  1;

  var $magic          = "Simsalabim";  ## Challenge seed
  var $database_class = "DB_Example";
  var $database_table = "auth_user";

  function auth_loginform() {
    global $sess;
    global $challenge;
    global $_PHPLIB;

$challenge = md5(uniqid($this->magic));
$sess->register("challenge");

include($_PHPLIB["libdir"] . "crloginform.ihtml");
  }

  function auth_validatelogin() {
    global $username, $password, $challenge, $response;


... etc.
  }

What this does is actually change the auth_login() method to use md5 passwords. So if I have $auth = new auth(), I am using plain text passwords, but if I have $auth = new Example_Challenge_Auth, I will be using md5 passwords.

[ahundiak]

HilFreddy,
Find a tutorial on using classes in php. There is one on phpbuilder and few others elsewhere. You are kind of on the right track but need some help on the details.

When class B extends class A it means that class B automatically gets all of the methods and variables contained in classs A. In general you would not create a object of class A any more, only class B.

So just to get started:

/* A table object */
class mysqlTable 
{
  var $dbtable;
  var $last_query;

  function mysqlTable($table)
  {
    $this->$dbtable = $table;
  }
  function select_all() 
  {
    $this->$last_query = "SELECT * FROM $this->dbtable";
    return $this->$last_query;
   }
}
/* phpBasic IS A table */
class phpBasic extends mysqlTable
{
  function phpBasic()
  {
    /* Call the parent constructor */
    $this->mysqlTable('basic_table_name');
  }
}
$basic = new phpBasic();
echo $basic->select_all();