Mastering PHP: From Basics to Building Dynamic Web Applications

Chapter 8: OOP in PHP & Final Project

🔹 1. Introduction

Object-Oriented Programming (OOP) in PHP allows you to organize code logically, reuse components, and scale efficiently. In this chapter, you'll learn PHP's OOP features and apply them in a final project — a basic Content Management System (CMS).

🔹 2. What Is OOP?

OOP organizes code around objects, which are instances of classes. A class defines the properties (data) and methods (functions) of the object.

✅ Key OOP Concepts:

🔹 3. Declaring Classes and Objects

✅ Basic Class:

class User {

  public $name = "Guest";

  public function sayHello() {

    return "Hello, " . $this->name;

  }

}

$user1 = new User();

$user1->name = "Alice";

echo $user1->sayHello(); // Hello, Alice

🔹 4. Constructors & __construct()

A constructor automatically runs when an object is created.

class Product {

  public $name;

  public $price;

  function __construct($name, $price) {

    $this->name = $name;

    $this->price = $price;

  }

  function display() {

    return "$this->name costs $this->price";

  }

}

$p = new Product("Laptop", 900);

echo $p->display();

🔹 5. Inheritance & Overriding

class Animal {

  public function makeSound() {

    echo "Some sound";

  }

}

class Dog extends Animal {

  public function makeSound() {

    echo "Bark!";

  }

}

$dog = new Dog();

$dog->makeSound(); // Bark!

🔹 6. Access Modifiers

class User {

  private $email;

  public function setEmail($email) {

    $this->email = $email;

  }

  public function getEmail() {

    return $this->email;

  }

}

🔹 7. Static Methods and Properties

Use static when a method or property doesn’t need a specific object.

class Math {

  public static function square($n) {

    return $n * $n;

  }

}

echo Math::square(5); // 25

🔹 8. Interfaces and Traits

✅ Interface:

interface Logger {

  public function log($msg);

}

class FileLogger implements Logger {

  public function log($msg) {

    echo "Log: $msg";

  }

}

✅ Trait:

trait Sharable {

  public function share() {

    echo "Shared!";

  }

}

class Post {

  use Sharable;

}

🔹 9. Final Project: Mini CMS (CRUD for Posts)

✅ Structure:

/cms

  ├── config.php

  ├── Post.php

  ├── index.php

  ├── create.php

  ├── update.php

  ├── delete.php

✅ config.php

<?php

$conn = new mysqli("localhost", "root", "", "cms");

if ($conn->connect_error) die("DB Error");

?>

✅ Post.php (Model Class)

class Post {

  private $conn;

  public function __construct($db) {

    $this->conn = $db;

  }

  public function getAll() {

    return $this->conn->query("SELECT * FROM posts");

  }

  public function create($title, $body) {

    $stmt = $this->conn->prepare("INSERT INTO posts (title, body) VALUES (?, ?)");

    $stmt->bind_param("ss", $title, $body);

    return $stmt->execute();

  }

  public function get($id) {

    return $this->conn->query("SELECT * FROM posts WHERE id=$id")->fetch_assoc();

  }

  public function update($id, $title, $body) {

    $stmt = $this->conn->prepare("UPDATE posts SET title=?, body=? WHERE id=?");

    $stmt->bind_param("ssi", $title, $body, $id);

    return $stmt->execute();

  }

  public function delete($id) {

    return $this->conn->query("DELETE FROM posts WHERE id=$id");

  }

}

✅ index.php (Read All)

require 'config.php';

require 'Post.php';

$post = new Post($conn);

$posts = $post->getAll();

while($row = $posts->fetch_assoc()) {

  echo "<h3>{$row['title']}</h3>";

  echo "<p>{$row['body']}</p><hr>";

}

You can add similar pages for:

• create.php — form to add a post
• update.php — edit existing post
• delete.php — delete a post by ID

✅ The project uses:

• OOP for model structure
• MySQL for storage
• Forms and file separation for MVC-like structure

✅ Summary Table: OOP & CMS Concepts