Association class

[PurpleMonkey]

Hello.

I've just got myself a copy of the PHP manual. (Very usefull, get it if you havn't already: www.php.net/download-docs.php) And I was curious as to what/how a class works. Anyway, I've had a read and I can't really make head nor tails of it. Could somebody take a second to tell me what a association/agrigation classes are. I had a go with the script that comes with the documentation, and it works, but I don't quite understand why only functions named the same as the class are called and others, arn't.

Thanks in advance, PM.

P.S, heres the code I tested:

<?php
class DateTime {

   function DateTime() 
   {
       // empty constructor
   }

   function now() 
   {
       return date("Y-m-d H:i:s");
   }
}

class Report {
   var $_dt;
   // more properties ...

   function Report() 
   {
       $this->_dt = new DateTime();
       // initialization code ...
   }

   function generateReport() 
   {
       $dateTime = $_dt->now();
       // more code ...
   }

   // more methods ...
}

$rep = new Report();
?> 

[drew010]

Basically, when you create a class, you are defining a new data type. The data type contains data members (the internale variables) that are pre-existing types (strings, integers, arrays...).

The functions in a class with the same name as the class, are called constructors. They get executed automatically when you create an object using the "new" keyword. Therefore, whatever you put inside the constructor, gets called upon creation. You can use it to initialize certain variables, get information about something, or you dont have to have one at all.

When talking about classes, association usually refers to two or more classes interacting with eachother, in one way or another. They could be getting information from eachother or updating eachother.
Aggregation, has to do with inheritance, which is creating a class using another class as the base. In aggregation you can think of a "has a" relationship, which you will learn about if you take a java or c++ programming class. For example you could have a class door, and then another class house. They could be related because a house "has a" door.
There are also "is a" relationships where classes are extended from another. If you had a really basic vehicle class, you could say an SUV "is a" vehicle, or a motorcycle "is a" vehicle.

If you have any other questions, just post back or email.

happy learning

[PurpleMonkey]

Thanks that makes alot more sense now!