Classes & Objects

Quick Introduction

Classes & Objects is a single PHP idea you'll use in almost every backend project.

In this lesson you learn only classes & objects — not five topics at once. By the end you can write a small working example and explain it in an interview.

We connect each lesson to our course projects: Login System, Blog CMS, REST API, Inventory, Employee Management, and E-Commerce Backend.

Business Problem

You're building the Employee Management. After a user signs in, you need classes & objects working correctly before storing data or showing a dashboard.

Without understanding Classes & Objects, the team ships bugs: wrong totals, broken sessions, or type errors that only appear in production. This lesson fixes that with one clear pattern you can copy into your project today.

Core Concept

• Classes & Objects is one focused idea — learn it before mixing with other PHP topics.
• Use it in PHP 8.3+ with declare(strict_types=1); at the top of every file.
• Our course project (Employee Management) uses classes & objects in real handlers.
• Run small scripts with php file.php after each change — don't just read.
• Interviewers ask for a one-minute explanation plus a tiny code sample.

Syntax

Core syntax for Classes & Objects. Every keyword below appears in production PHP — Laravel and Symfony use the same primitives under the hood.

declare(strict_types=1);

Keywords: declare · strict_types · namespace

Step-by-Step Example

Run this script locally. Change one value, run again, and watch what changes.

<?php
declare(strict_types=1);

namespace App\Models;

final class User {
    private(set) int $loginCount = 0;

    public function __construct(
        public readonly string $email,
        private string $displayName,
    ) {}

    public function recordLogin(): void {
        $this->loginCount++;
    }

    public function greeting(): string {
        return "Hello, {$this->displayName} (#{$this->loginCount} logins)";
    }
}

$user = new User('dev@example.com', 'Alex');
$user->recordLogin();
echo $user->greeting();

Line by line

1. — part of the classes & objects example; run the file to see the result.
2. declare(strict_types=1); — turns on strict type checking for this file.
3. namespace App\Models; — part of the classes & objects example; run the file to see the result.
4. final class User { — part of the classes & objects example; run the file to see the result.
5. private(set) int $loginCount = 0; — part of the classes & objects example; run the file to see the result.

{"status":"ok"}

Real-World Example

In the Employee Management, classes & objects appears in a single request handler — not spread across ten files. Keep the example small, test it with php, then paste the pattern into your project branch.

<?php
declare(strict_types=1);

// TODO: Classes & Objects exercise for Employee Management