Question

Can you please explain the classes and objects in PHP?

I know they are the core of understanding the OOP in Php (Object-oriented programming)

Thanks

P.S. If you can also give examples of their usage with code... thanks

Answer 1

In PHP classes provide the structure for objects and act as template for objects of the same type. Functions used in Class are called methods, the variables are called properties;

Class:

• Use keyword new to create objects and invoke constructors
• A class can have many instances (objects)
• Use PascalCase for Class naming
• Class is made up of state and behavior
• Getters and Setters provide access to the fields
• Functions describe behaviour
• Fields store values
• Fields (private variables), e.g. day, month, year
• Data, e.g. getDay, setMonth, getYear
• Actions (behavior), e.g. plusDays(count), subtract(date)

One class may have many instances (objects)

• Sample class: DateTime
• Sample objects: peterBirthday, mariaBirthday

Objects:

• Objects are Instances of Classes
• Creating the object of a defined class is called instantiation
• The instance is the object itself, which is created runtime

All instances have common behaviour:

$date1 = new DateTime();
$date2 = new DateTime();
$date3 = new DateTime();

On the picture below you can see more about the Class, Objects:

Here is one example taken from this video: https://www.youtube.com/watch?v=yrIbbKuSqK8

<?php

class Game
{
    var $price;
    var $name;
    var $photo;
    var $dir = "games/";

    public function print_game() {
        echo $this->name . PHP_EOL;
        echo $this->price . PHP_EOL;
        echo $this->dir . $this->photo . PHP_EOL;
    }

    public function set_game($name, $price, $photo) {
        $this->name = $name;
        $this->price = $price;
        $this->photo = $photo;
    }
}

$game = new Game();

$game->name = "Metro";
$game->price = 49;
$game->photo = "metro.jpg";

$game->print_game();//1st game: Metro (printing)

$game->name = "Detroit Become Human";
$game->price = 59;
$game->photo = "detroit.jpg";

$game->print_game();//2nd game: Detroit Become Human (printing)

$game->set_game("Little Big Planet 3", 49, "lbp3.jpg");

$game->print_game();//3rd game: Little Big Planet 3 (printing)

and the output: