PHP Project Documentation: Advanced Methods and Tools

Introduction: Why Documentation Is the Code You Write for Yourself a Month Later

Every PHP developer has at least once encountered a situation where their own code, written a couple of months ago, seems foreign and incomprehensible. At an advanced development level, documentation ceases to be just comments — it becomes part of the project architecture, a tool for automatically generating API references, and a foundation for teamwork. In this article, we will explore how to create documentation for PHP projects that will be useful not only for beginners but also for experienced developers working with large codebases.

We will discuss PHPDoc standards (PSR-5 and PSR-19), automatic generation tools (phpDocumentor, Doxygen), as well as how to structure documentation for complex projects using interfaces, traits, and abstract classes.

PHPDoc Standards: PSR-5 and PSR-19

For professional PHP documentation, it is necessary to adhere to accepted standards. The main ones are PSR-5 (PHPDoc) and PSR-19 (PHPDoc Tags). PSR-5 defines the syntax and structure of documentation blocks, while PSR-19 defines the list of recommended tags.

Basic Tags and Their Advanced Usage

In addition to the obvious @param, @return, and @throws, at an advanced level the following are actively used:

\n
• @method — for describing magic methods (__call, __get);
\n
• @property — for describing magic properties;
\n
• @template — for generic programming (generics);
\n
• @implements and @extends — for explicitly specifying inheritance;
\n
• @internal — for marking code not intended for external use.
\n

<?php\n\n/**\n * @template T of object\n * @implements CollectionInterface<T>\n */\nclass EntityCollection implements CollectionInterface\n{\n    /**\n     * @param array<int, T> $items\n     */\n    public function __construct(\n        private array $items = []\n    ) {}\n\n    /**\n     * @return T|null\n     */\n    public function first(): ?object\n    {\n        return $this->items[0] ?? null;\n    }\n\n    /**\n     * @method void sortBy(string $field)\n     * @method T get(int $index)\n     */\n    public function __call(string $name, array $arguments): mixed\n    {\n        // Magic method implementation\n    }\n}\n

Typing in PHPDoc: From Simple to Complex

Advanced documentation requires precise type descriptions. Use:

\n
• array<int, string> — associative array;
\n
• Collection<User> — collection of objects;
\n
• Closure(User): bool — closure with argument and return type descriptions;
\n
• class-string<User> — a string containing a class name.
\n

Example of proper documentation for a complex method:

/**\n * Filters the user collection by a given condition.\n *\n * @param Closure(User): bool $callback Filter function\n * @return static<User> New collection with filtered elements\n *\n * @throws InvalidArgumentException if callback is not callable\n *\n * @example\n * $admins = $users->filter(fn(User $u) => $u->isAdmin());\n */\npublic function filter(Closure $callback): static\n{\n    // ...\n}\n

Automatic Documentation Generation: phpDocumentor and Doxygen

Manually keeping documentation up to date is a task that quickly becomes overwhelming. Automatic generation tools allow you to create HTML, PDF, or Markdown documentation directly from PHPDoc blocks.

phpDocumentor (phpdoc)

The most popular tool for PHP. Installation via Comp