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Q: Classes and Objects in PHP

+4 votes
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)


P.S. If you can also give examples of their usage with code... thanks
asked in PHP category by user mitko

1 Answer

+3 votes

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;


  • 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 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:

classes and objects in php

Here is one example taken from this video:


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:

classes objects php output

answered by user ak47seo