classes - what are they?

[dclamp]

what are classes in php? How are they used. I have seen them, just dont understand how they work.

what is "->" used for?

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The class is central to object orientated design methodology. In object orientated design you build a systems by putting together a set of objects. Much like a body contains many organs; each doing there own thing to accomplish a task and made to work together to form an organism.

In object orientated design; an object usually represents a single entity within the system (i.e: an order). The object can execute its own precesses (methods) and communicate with other objects via its state (properties).

A class is simply a template for an object. It describes how it behaves and how it should interact with other objects in a system. You use a class to create an instance of an object.

class Human
{
    const GENDER_MALE = 1;
    const GENDER_FEMALE = 2;

    private $dob;
    private $gender;
    private $children = array ();
    private $mother;
    private $father;

    public function __construct($gender)
    {

        $dob = Now();
    $this->gender = $gender;
    }

    public function reproduce(Human $partner, $noChildren)
    {
        if ($partner->getGender() == $this->gender()) {
            thrw new Exception('This version of humanity does not support same sex couples.');
        }

    if ($this->gender == self::GENDER_MALE) {
        $mother = $partner;
        $father = $this;
    } else {
        $mother = $this;
        $father = $partner;
    }

    for ($x = 1; $x<=$noChildren; $x++) {
        $child = = new Human(rand(GENDER_MALE, GENDER_FEMALE);
        $child->setMother($mother);
        $child->setFather($father);
            $this->children[] )
        }
    }

    public function getGender()
    {
    return $this-> gender;
    }

    public function getMother()
    {
    return $this->mother;
    }

    public function getFather()
    {
    return $this->father;
    }

    public function setMother(Human $mother)
    {
    if ($mother->getGender() != self::GENDER_FEMALE) {
        throw new Exception ('Gender Adnormality');
    }

    $this->mother = $mother;
    }

    public function setFather(Human $father)
    {
    if ($father->getGender() != self::GENDER_MALE) {
        throw new Exception ('Gender Adnormality');
    }

    $this->father = $father;
    }

    public function getDOB()
    {
    return $this->dob;
    }

    public function getChildren()
    {
    return $this->children;
    }
} 

The above example demonstrates a simple class called Human. Disregarding the simplistic and possibly biased view of humanity. The functions in the class represent methods reproduce() is a defined behaviour. The getXXXXX() methods are accessors/getters and allow you to access properties declared as private (private means only accessible within the object).

-> is the object access operator $o->function() executes a method $o->property returns a public property. The :: operator is the scope resolution operator. This is used to access constant and static properties and methods.

You create an instance of an object using the new operator:

$male = new Human(Human::GENDER_MALE);
$female =  new Human(Human::GENDER_FEMALE);

$male->reproduce($female, 4); 

The benefits of object orientated design are clear. Firstly you can encapsulate data and hence protect it inside an object by declaring it private. There are three others too which I let you read up on:

• Encapsulation.
• Polymorphism.
• Inheritance.
• Abstraction.

OOP is the best thing since sliced bread. I recommend it to any web developer in conjunction with the MVC design pattern.

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P.s: Read the PHP5 OOP tutorial in my sig

[dclamp]

wow. Ok, thanks va!