[landing]

I've just started teaching myself OOP in PHP.

I've created a database class, which I can use for connecting to the DB, selecting a DB, running queries etc.

My question is, how can I use this object within other objects? I have created a few other objects which contain functions for looking up records in the database. I want to be able to use my Database class to run the queries.


Any enlightenment would be greatly appreciated.

Thanks in advance

[Patiek]

There are a few ways (depending on class structure). However, your class is probably going to be using syntax similar to:

$DB = new YourDatabaseClass(...);
$DB->query("your query");


and so on from within your other classes. If you only need / have the one database or database object then you can go about passing in that database via constructor (a function within your class with same name as your class that is called when you class is initialized).

I am really not sure what else you are going after, so here is a basic example of what I am talking about (although you can approach this in many different ways). The one thing I would discourage is the use of globals (such as using "global $DB;" ). Also, the style below should be PHP 4 friendly.

PHP Code:

<?php



class YourFirstClass

{

    var $DB;

    var $someObject;



    function YourFirstClass()

    {

        // initialize your database object

        $this->DB = new YourDatabaseClass(...);



        // initialize some other class

        $this->someObject = new YourSecondClass($this->DB);

    }



    function doSomething()

    {

        $this->DB->query("whatever");

        .....

    }

}





class YourSecondClass

{

    var $DB;



    function YourSecondClass(&$DB)

    {

        // we do not want to replicate object, so we use &

        $this->DB  =& $DB;

    }



    function doSomething()

    {

        $this->DB->query("whatever else");

        ...

    }

}





class YourDatabaseClass

{

    ... whatever your database class has...

}

If you like I can also post a database class that I use, just ask.

[darksystem]

try also the inheritance functionality of OOP

e.g.
Your created class for your DB

class DB {

}


This class will inherits your class DB including its vars and methods or proporties.

class test extends DB
{

}

got it?

PS: I suggest your better read the Classes and Objects of the phpmanual.
You can download here
http://www.php.net/download-docs.php

Hope it helps.

[landing]

Thanks Patiek and darksystem. Very helpful!

OOP is a whole new world to me, but I'm eager to learn because I've already realised the benefits.

Time to start some serious reading...

[duesi]

And if you put your class in a different file you need to include it first:

PHP Code:

include_once("db.lib.php");



$db = new db();

$count = $db->query("SELECT COUNT(*) FROM my_table");

... 

I keep all my classes in a separate file, this keeps my head free.
I think this is what OO is mainly about: you do not need to think about implementation details. $db provides a service (maipulating a DB), but you don't care about the inner workings of that service (at least after you have written the class).

Happy Coding!