Documentation in PHP: How to Write Code You're Not Ashamed to Show

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Your code speaks louder than words? No, if you're writing in PHP

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Imagine: you open an old PHP project you wrote six months ago. You look at the function processData() and understand... absolutely nothing. What data? Where does it come from? Why is the method called doMagic()? Sound familiar? If so, this article is for you.

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Good documentation in PHP is not just "politeness" towards colleagues. It's your insurance policy against headaches, it accelerates the onboarding of new developers, and ultimately, it's the quality of your product. In this article, we'll break down the best practices for documenting PHP code that will turn your chaotic code into a coherent, understandable system.

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Why Documentation in PHP is Not "Extra Work"

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Many developers believe that "good code speaks for itself." This is only partially true. Good code explains how it works, but it rarely explains why and why exactly this way. Documentation fills these gaps. It answers the questions:

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What input data does the function expect?
What does it return in case of an error?
Why was a particular architectural decision made?
What side effects does the method have?

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Without answers to these questions, your code is a black box. And even experienced developers are afraid to touch black boxes.

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PHPDoc: Your Main Tool

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The de facto standard for documenting PHP code is PHPDoc. It's a special comment format that starts with /** and ends with */. It is supported by all modern IDEs (PhpStorm, VS Code) and documentation generation tools like phpDocumentor or Doxygen.

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The basic PHPDoc syntax includes:

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@param — description of method or function parameters
@return — type and description of the return value
@throws — which exceptions the method can throw
@var — type of a class property
@see — link to a related method or class
@deprecated — marks functionality as outdated

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Example of a Good PHPDoc Block

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<?php\n\n/**\n * Calculates the final order price considering discounts and taxes.\n *\n * This method applies a progressive discount scale based on the order amount.\n * If the amount exceeds 10,000 rubles, a maximum discount of 15% is applied.\n *\n * @param float $basePrice Base order price without discounts (in rubles).\n * @param float $taxRate   Tax rate, e.g., 0.20 for 20%.\n * @param string $currency Currency for formatting the result (default 'RUB').\n *\n * @return string Formatted string with the final price, e.g., "12 500.00 ₽".\n *\n * @throws \\InvalidArgumentException If the base price is negative.\n * @throws \\RuntimeException         If the currency exchange rate cannot be obtained.\n *\n * @see \\PriceCalculator::applyDiscounts() For details on discount calculation.\n */\npublic function calculateFinalPrice(float $basePrice, float $taxRate, string $currency = 'RUB'): string\n{\n    if ($basePrice < 0) {\n        throw new \\InvalidArgumentException('Base price cannot be negative.');\n    }\n    // ... calculation logic\n}

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Notice: we didn't just list the types, but also explained the context (progressive scale), the format (formatted string), and the boundary conditions (exceptions). This is what quality documentation looks like.

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