URL Shortener

Quick Introduction

URL Shortener is a single PHP idea you'll use in almost every backend project.

In this lesson you learn only url shortener — 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 E-Commerce Backend. After a user signs in, you need url shortener working correctly before storing data or showing a dashboard.

Without understanding URL Shortener, 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

• URL Shortener 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 (E-Commerce Backend) uses url shortener 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 URL Shortener. 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);

final class UrlShortener {
    public function __construct(private \PDO $pdo, private string $baseUrl) {}

    public function shorten(string $longUrl): string {
        $code = substr(bin2hex(random_bytes(6)), 0, 8);
        $stmt = $this->pdo->prepare('INSERT INTO links (code, url, created_at) VALUES (:c, :u, NOW())');
        $stmt->execute(['c' => $code, 'u' => $longUrl]);
        return $this->baseUrl . '/' . $code;
    }

    public function resolve(string $code): ?string {
        $stmt = $this->pdo->prepare('SELECT url FROM links WHERE code = :c LIMIT 1');
        $stmt->execute(['c' => $code]);
        return $stmt->fetchColumn() ?: null;
    }
}

$svc = new UrlShortener(new PDO('mysql:host=127.0.0.1;dbname=links', 'app', ''), 'https://sho.rt');
echo $svc->shorten('https://example.com/docs/php-8.3');

Line by line

1. — part of the url shortener example; run the file to see the result.
2. declare(strict_types=1); — turns on strict type checking for this file.
3. final class UrlShortener { — part of the url shortener example; run the file to see the result.
4. public function __construct(private \PDO $pdo, private string $baseUrl) {} — part of the url shortener example; run the file to see the result.
5. public function shorten(string $longUrl): string { — part of the url shortener example; run the file to see the result.

Authenticated

Real-World Example

In the E-Commerce Backend, url shortener 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: URL Shortener exercise for E-Commerce Backend