PHP OOP – Access Modifiers

Understanding PHP OOP Access Modifiers: A Comprehensive Guide

Introduction:

In PHP Object-Oriented Programming (OOP), access modifiers play an important role in controlling the visibility of properties and methods within classes. By understanding how access modifiers work, developers can enhance the encapsulation and security of their code. This toturial guide will go into the concepts of public, protected, and private access modifiers in PHP OOP, providing clarity and practical examples for mastering this essential aspect of object-oriented programming.

In PHP Object-Oriented Programming (OOP), access modifiers are keywords used to specify the accessibility of properties and methods within a class.

There are three main access modifiers in PHP:

public access modifiers:

Public members are accessible from anywhere, both inside and outside the class.

protected access modifiers :

Protected members are accessible within the class itself and by classes that extend the current class (subclasses).

private access modifiers:

Private members are only accessible within the class itself.
They cannot be accessed by subclasses or from outside the class.

How to use access modifiers in PHP?

Below is an example showing the usage of these access modifiers in PHP:

class MyClass {
public $publicVar = "Public variable";
protected $protectedVar = "Protected variable";
private $privateVar = "Private variable";

public function publicMethod() {
echo "This is a public method<br>";
}

protected function protectedMethod() {
echo "This is a protected method<br>";
}

private function privateMethod() {
echo "This is a private method<br>";
}

public function accessMembers() {
echo $this->publicVar . "<br>"; // Accessible
echo $this->protectedVar . "<br>"; // Accessible within the class
echo $this->privateVar . "<br>"; // Accessible within the class
$this->publicMethod(); // Accessible
$this->protectedMethod(); // Accessible within the class
$this->privateMethod(); // Accessible within the class
}
}

$obj = new MyClass();
echo $obj->publicVar . "<br>"; // Accessible
// echo $obj->protectedVar; // Not accessible from outside the class
// echo $obj->privateVar; // Not accessible from outside the class
$obj->publicMethod(); // Accessible
// $obj->protectedMethod(); // Not accessible from outside the class
// $obj->privateMethod(); // Not accessible from outside the class

$obj->accessMembers(); // Accessing all members from within the class

Exaplanation:

In the example above, we can see how public, protected, and private members are declared and accessed within a class.
Access to these members varies based on their respective access modifiers.

Step by step How to use PHP OOP – Access Modifiers?

we will go through a step-by-step example of how to use access modifiers in PHP OOP:

Step 1: Define a class with properties and methods:

class MyClass {
public $publicVar = "Public variable";
protected $protectedVar = "Protected variable";
private $privateVar = "Private variable";

public function publicMethod() {
echo "This is a public method<br>";
}

protected function protectedMethod() {
echo "This is a protected method<br>";
}

private function privateMethod() {
echo "This is a private method<br>";
}
}

Step 2:Create an object of the class:

$obj = new MyClass();

Step 3:Access public members (properties and methods) from outside the class:

echo $obj->publicVar . "<br>"; // Accessible
$obj->publicMethod(); // Accessible

Step 4:

Attempt to access protected and private members from outside the class (will result in an error):

// echo $obj->protectedVar; // Not accessible from outside the class
// echo $obj->privateVar; // Not accessible from outside the class
// $obj->protectedMethod(); // Not accessible from outside the class
// $obj->privateMethod(); // Not accessible from outside the class

Step 5:
Access all members (public, protected, and private) from within the class:

$obj->accessMembers(); // Method defined within the class to access all members

Step 6:
Define a method within the class to access all members:

public function accessMembers() {
echo $this->publicVar . "<br>"; // Accessible
echo $this->protectedVar . "<br>"; // Accessible within the class
echo $this->privateVar . "<br>"; // Accessible within the class
$this->publicMethod(); // Accessible
$this->protectedMethod(); // Accessible within the class
$this->privateMethod(); // Accessible within the class
}

Step 7:

Running the script should output:

Public variable
This is a public method
Public variable
Protected variable
Private variable
This is a public method
This is a protected method
This is a private method

This shows how access modifiers control the accessibility of class members in PHP OOP.

complete code example about PHP OOP – Access Modifiers

We will create a complete code example of a PHP web page showing the usage of access modifiers in Object-Oriented Programming:

<!DOCTYPE html>
<html>
<head>
<title>PHP OOP - Access Modifiers Example</title>
</head>
<body>
<?php
class MyClass {
public $publicVar = "Public variable";
protected $protectedVar = "Protected variable";
private $privateVar = "Private variable";

public function publicMethod() {
echo "This is a public method<br>";
}

protected function protectedMethod() {
echo "This is a protected method<br>";
}

private function privateMethod() {
echo "This is a private method<br>";
}

public function accessMembers() {
echo $this->publicVar . "<br>"; // Accessible
echo $this->protectedVar . "<br>"; // Accessible within the class
echo $this->privateVar . "<br>"; // Accessible within the class
$this->publicMethod(); // Accessible
$this->protectedMethod(); // Accessible within the class
$this->privateMethod(); // Accessible within the class
}
}

$obj = new MyClass();

echo "<h2>Accessing Public Members:</h2>";
echo $obj->publicVar . "<br>"; // Accessible
$obj->publicMethod(); // Accessible

echo "<h2>Accessing Protected and Private Members:</h2>";
// Attempting to access protected and private members from outside the class (will result in an error):
// echo $obj->protectedVar; // Not accessible from outside the class
// echo $obj->privateVar; // Not accessible from outside the class
// $obj->protectedMethod(); // Not accessible from outside the class
// $obj->privateMethod(); // Not accessible from outside the class

echo "<h2>Accessing Members from Within the Class:</h2>";
$obj->accessMembers(); // Method defined within the class to access all members
?>
</body>
</html>

You can save this code in a PHP file (e.g., access_modifiers_example.php) and open it in your web browser to see the output.

This example shows how access modifiers control the accessibility of class members within PHP OOP, both inside and outside the class.

A project about PHP OOP – Access Modifiers

Step by step how to create aproject using PHP OOP – Access Modifiers

Creating a project using PHP OOP with access modifiers involves several steps as the following:

Step 1: Set up your development environment:

Ensure you have PHP installed on your system. You can download it from the official PHP website (https://www.php.net/downloads).

Choose a text editor or an Integrated Development Environment (IDE) for coding. Some popular options include Visual Studio Code, Sublime Text, PHPStorm, etc.
Set up a web server environment such as Apache or Nginx to run your PHP scripts. Alternatively, you can use local development environments like XAMPP, WAMP, or MAMP, which come bundled with Apache, PHP, and MySQL.

Step 2: Create a directory for your project:

Create a folder for your project. You can name it something like “oop_access_modifiers_project”.

Step 3: Define your class with access modifiers:

Create a PHP file within your project folder. For example, MyClass.php.
Define your class with properties and methods, including different access modifiers (public, protected, private).

<?php
class MyClass {
public $publicVar = "Public variable";
protected $protectedVar = "Protected variable";
private $privateVar = "Private variable";

public function publicMethod() {
echo "This is a public method<br>";
}

protected function protectedMethod() {
echo "This is a protected method<br>";
}

private function privateMethod() {
echo "This is a private method<br>";
}

public function accessMembers() {
echo $this->publicVar . "<br>"; // Accessible
echo $this->protectedVar . "<br>"; // Accessible within the class
echo $this->privateVar . "<br>"; // Accessible within the class
$this->publicMethod(); // Accessible
$this->protectedMethod(); // Accessible within the class
$this->privateMethod(); // Accessible within the class
}
}
?>

Step 4: Create a PHP script to utilize the class:

Create another PHP file within your project folder. For example, index.php.
Include the class file (MyClass.php).
Create an object of the class and shows the usage of access modifiers.

<?php
require_once 'MyClass.php';

$obj = new MyClass();

echo "<h2>Accessing Public Members:</h2>";
echo $obj->publicVar . "<br>"; // Accessible
$obj->publicMethod(); // Accessible

echo "<h2>Accessing Protected and Private Members:</h2>";
// Attempting to access protected and private members from outside the class (will result in an error):
// echo $obj->protectedVar; // Not accessible from outside the class
// echo $obj->privateVar; // Not accessible from outside the class
// $obj->protectedMethod(); // Not accessible from outside the class
// $obj->privateMethod(); // Not accessible from outside the class

echo "<h2>Accessing Members from Within the Class:</h2>";
$obj->accessMembers(); // Method defined within the class to access all members
?>

Step 5: Run your project:

Start your web server.
Open your web browser and navigate to the URL where your project is located (e.g., http://localhost/oop_access_modifiers_project).
You should see the output demonstrating the usage of access modifiers within your PHP OOP project.
That’s it! You’ve created a simple PHP project demonstrating the usage of access modifiers in Object-Oriented Programming. You can expand upon this project by adding more classes, methods, and functionalities as needed.

Quiz about about PHP OOP access modifiers with answers

we will create a simple quiz based on the lesson about PHP OOP access modifiers:

Quiz: PHP OOP Access Modifiers

1-What are the three main access modifiers in PHP OOP?

A) public, protected, private
B) open, secure, restricted
C) global, local, private
D) accessible, restricted, private
Answer: A) public, protected, private

2-Which access modifier makes class members accessible from anywhere, both inside and outside the class?

A) public
B) protected
C) private
D) accessible
Answer: A) public

3-Which access modifier restricts access to class members only within the class itself and by classes that extend the current class (subclasses)?

A) public
B) protected
C) private
D) accessible
Answer: B) protected

4-Which access modifier restricts access to class members only within the class itself?

A) public
B) protected
C) private
D) accessible
Answer: C) private

5-Which of the following statements is true regarding access modifiers in PHP OOP?

A) Private members are accessible from outside the class.
B) Protected members are accessible only within the class itself.
C) Public members are accessible only within the class itself.
D) Access modifiers in PHP OOP have no effect on the accessibility of class members.
Answer: B) Protected members are accessible only within the class itself.

6-In PHP OOP, what keyword is used to specify a public member or method?

A) open
B) public
C) global
D) accessible
Answer: B) public

7-In PHP OOP, what keyword is used to specify a protected member or method?

A) open
B) public
C) protected
D) accessible
Answer: C) protected

8-In PHP OOP, what keyword is used to specify a private member or method?

A) open
B) public
C) private
D) accessible
Answer: C) private

9-Which access modifier would you use if you want a property or method to be accessible only within the class itself, but not by any subclasses?