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Creating a Class

In this lesson, we will create a class, which remember, is basically a blueprint for creating objects. We will then create an object from that class and access its properties and methods. The process of creating an object from a class is called instantiation.

Let's create a class called User either in the sandbox files or in your own file:

class User
{
    // Class body
}

We use the class keyword to create a class. The class name should be in PascalCase, which means the first letter of each word should be capitalized. The class body is enclosed in curly braces.

Adding Properties​

A property is basically a variable or an attribute that belongs to a class. We can add properties to our class like this:

class User
{
    public $name;
    public $email;
}

Here, we have added two properties to our User class: $name and $email. We use the public keyword to specify the visibility of the property. We will learn more about visibility in the next lesson. For now, just know that public means the property can be accessed from outside the class.

Default Values​

We can also set default values for our properties:

class User
{
    public $name = 'John Doe';
    public $email = 'john@gmail.com';
}

Adding Methods​

A method is basically a function that belongs to a class. We can add methods to our class like this:

class User
{
    public $name;
    public $email;

    public function login()
    {
        echo 'The user logged in.';
    }
}

Here, we have added a method called login to our User class.

Instantiating an Object​

Now that we have a very basic User class, let's create an object from it:

$user1 = new User();

We use the new keyword to create an object from a class. The variable $user1 now holds an object of the User class. We can access the properties and methods of the object using the arrow operator (->):

$user1->name = 'John Doe';
$user1->email = 'john@gmail.com';

echo $user1->name; // John Doe
echo $user1->email; // john@gmail.com

We can also call the login method on the object:

$user1->login(); // The user logged in.

The constructor method​

The constructor method is a special method that is called automatically when an object is instantiated. We can use it to set the initial state of the object. In the code that we have written, we first instantiated a user object and then set its name and email properties. We can simplify this process by passing the name and email as arguments to the constructor method:

class User
{
    public $name;
    public $email;

    public function __construct($name, $email)
    {
        $this->name = $name;
        $this->email = $email;
    }

    public function login()
    {
        echo 'The user logged in.';
    }
}

this keyword​

In the constructor method, we used the $this keyword to set the name and email properties. The $this keyword refers to the current object. So when we say $this->name, we are referring to the name property of the current object. We will learn more about $this as we go along.

Now, instead of assigning the name and email properties after instantiating the object, we can pass them as arguments to the constructor method:

$user1 = new User('John Doe', 'john@gmail.com');

We can create as many users as we want from this class. Let's create another instance:

$user2 = new User('Jane', 'jane@gmail.com');

We can now get any property or call any methods on these objects:

echo $user1->name; // John Doe
echo $user2->name; // Jane

$user1->login(); // The user logged in.
$user2->login(); // The user logged in.

Using this in methods​

We can use the $this keyword in methods as well. Let's change the login method to use the $this keyword:

public function login() {
    echo $this->name . ' logged in.';
}

Now if we call the login method on the $user1 object, it will echo John Doe logged in. If we call it on the $user2 object, it will echo Jane logged in. This is because it pertains to the current object.

Now that we know how to create classes with properties, methods and a constructor, let's look at visibility in the next lesson.