phpapprentice/chapters/basics/11-classes.md

Classes allow you to define your own data types. All classes start with the class keyword followed by the name of the class and opening and closing curly braces.

<?php

class Car
{
}

To create an instance of a class, you use the new keyword in front of the class name with parentheses.

$car = new Car();

A class can define attributes and methods. An attribute is a piece of data stored on the class instance. You can define an attribute by adding the word public and a variable name inside the class definition.

class Bicycle
{
    public $color;
}

Then, when you create an instance of the class, you can set and use the attribute on the instance using ->.

$bike = new Bicycle();
$bike->color = 'Blue';
echo $bike->color . "\n";

An instance of a class is called an object. Congratulations! You are now performing object-oriented development.

$redBike = new Bicycle();
$redBike->color = 'Red';
echo $redBike->color . " Bike Object\n";

A method is a function attached to the class. You can add a method to a class by using the public keyword followed by the function. A method can access the attributes and methods of an object instance using the $this variable.

class Tricycle
{
    public $color;

    public function echoColor()
    {
        echo $this->color . "\n";
    }
}

You can execute a method on an object using the same -> arrow characters with parentheses after the method name.

$bike = new Tricycle();
$bike->color = 'Red';
$bike->echoColor();