PHP Project Documentation: A Complete Guide to Writing

Introduction: Why Documentation is Needed in PHP Projects?

Quality documentation is not a luxury, but a necessity for any PHP project, whether it's a small framework, library, or large web application. Well-written documentation saves hours of development, simplifies onboarding for new team members, and helps avoid many errors. According to a JetBrains survey, more than 60% of developers consider lack of documentation one of the main problems when working with someone else's code.

In this article, we will break down how to properly organize the process of writing documentation for a PHP project: from basic code comments to full-fledged technical documentation generation. You will learn about the PHPDoc standard, best formatting practices, and automation tools.

PHPDoc Basics: Documenting Code Correctly

PHPDoc is a standard for annotating PHP code that allows you to describe types, parameters, return values, and exceptions. It is understood by most IDEs (PhpStorm, VS Code) and documentation generation tools.

DocBlock Structure

Each DocBlock starts with /** and ends with */. Inside, lines start with *. Here is the minimum set of tags:

• @param — description of a function/method parameter
• @return — description of the return value
• @throws — exceptions that the method may throw
• @var — type of a class property
• @see — link to a related element

<?php/** * Calculates the final price of a product considering a discount. * * @param float $basePrice Base price of the product * @param float $discountPercent Discount percentage (from 0 to 100) * @return float Final price after applying the discount * @throws InvalidArgumentException If the discount percentage is outside the 0-100 range * * @see applyCoupon() */function calculateFinalPrice(float $basePrice, float $discountPercent): float{    if ($discountPercent < 0 || $discountPercent > 100) {        throw new InvalidArgumentException('Discount must be between 0 and 100%');    }    return $basePrice * (1 - $discountPercent / 100);}?>

Documenting Classes and Interfaces

For classes, use the @property tag (for magic properties), @method (for magic methods), and @template (for generic types).

<?php/** * Repository for working with users. * * @template T of User * @method User|null findById(int $id) Find a user by ID * @property-read int $count Number of users */class UserRepository{    /**     * @var array<int, T> User storage     */    private array $users = [];

    /**     * Adds a user to the repository.     *     * @param T $user User object     * @return int ID of the added user     */    public function add(User $user): int    {        // implementation    }}?>

Automatic Documentation Generation: phpDocumentor and Doxygen

Manually creating HTML documentation is a labor-intensive process. Fortunately, there are tools that generate it automatically from PHPDoc comments.

phpDocumentor (phpDoc)

The most popular tool for PHP. It is installed via Composer:

composer require --dev phpdocumentor/phpdocumentor

Running the generation:

vendor/bin/phpdoc -d ./src -t ./docs

Where -d is the directory with the source code, and -t is the folder for the finished documentation.

Configuration Setup

Create a phpdoc.xml file in the project root:

<?xml version="1.0" encoding="UTF-8"?><phpdocumentor>    <title>My PHP Project</title>    <paths>