Writing Documentation for a PHP Project: From A to Z

Introduction

Documentation is not just a nice addition to a project, but a critically important element of professional PHP development. Well-written documentation accelerates the onboarding of new developers, reduces the number of errors, and makes code maintainable even years later. In this article, we will go from the basics of writing comments to creating full-fledged technical documentation for your PHP project.

We will break down PHPDoc standards, best formatting practices, automatic generation tools, and answer the question: how to make documentation useful, not just formal.

PHPDoc Basics: How to Properly Comment PHP Code

The PHPDoc standard (or DocBlock) is a generally accepted way of documenting PHP code. It is based on special comments that start with /** and end with */. Each such block describes a code element: a class, method, property, or function.

Basic DocBlock Structure

A minimal documentation block includes a description and a set of tags (annotations). Let's look at an example for a simple method:

<?php\n\n/**\n * Calculates the sum of two numbers.\n *\n * @param int $a The first addend.\n * @param int $b The second addend.\n * @return int The sum of the numbers.\n */\nfunction sum(int $a, int $b): int {\n    return $a + $b;\n}\n?>

Main PHPDoc Tags

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• @param — describes a method or function parameter. Format: @param type $name Description.
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• @return — specifies the return type and its description.
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• @var — used for class properties to indicate their type.
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• @throws — documents exceptions that a method may throw.
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• @see — a link to another documentation element or an external resource.
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• @deprecated — marks an element as deprecated, with an indication of an alternative.
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Example for a class with multiple tags:

<?php\n\n/**\n * Class for working with a database.\n *\n * @package App\\Database\n * @author  Ivan Ivanov\n * @version 1.0.0\n */\nclass Database {\n    /**\n     * @var PDO Database connection.\n     */\n    private PDO $connection;\n\n    /**\n     * Establishes a connection to the database.\n     *\n     * @param string $dsn  The DSN connection string.\n     * @param string $user The username.\n     * @param string $pass The password.\n     *\n     * @throws PDOException If connection fails.\n     */\n    public function connect(string $dsn, string $user, string $pass): void {\n        $this->connection = new PDO($dsn, $user, $pass);\n    }\n}\n?>

Tools for Generating PHP Documentation

Manually maintaining documentation in HTML format is inefficient. Automatic generators come to the rescue. The most popular one is phpDocumentor (phpdoc).

Installing and Basic Usage of phpDocumentor

You can install phpDocumentor via Composer:

composer require --dev phpdocumentor/phpdocumentor

After installation, run the documentation generation from the project root:

vendor/bin/phpdoc -d src -t docs

Where -d src is the folder with the source code, and -t docs is the folder where the generated HTML documentation will be saved.

Other Useful Tools

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• Doxygen — supports not only PHP but also C++, Python, Java. Suitable for projects in mixed languages.
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• Sami — a modern documentation generator that can create multiple versions of documentation for different code branches.
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• ApiGen — a lightweight generator focused on ease of use.
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Best Practices for Writing PHP Documentation

High-quality documentation is