Avoiding Primitive Obsession in PHP

How Value Objects Help You Write Safer, Clearer, and More Expressive Domain Code

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Keywords: php, primitive obsession, value object, domain-driven design, clean code, refactoring, php 8, types, money object, email value object, php arrays, laravel, symfony

1. “Everything Is a String”: The Hidden Smell in PHP Codebases

PHP makes it incredibly easy to start shipping features.

• Need an email? Just use a string.
• Need a price? Eh, float is fine.
• Need some user data? Just throw stuff in an array.

It feels fast — until it doesn’t.

You start seeing functions like this:

function registerUser(
    string $email,
    string $password,
    string $firstName,
    string $lastName,
    string $countryCode
) {
    // ...
}

Or service methods like:

public function createDiscount(
    string $code,
    float $amount,
    string $currency,
    string $type,
    int $expiresAtTimestamp
): void {
    // ...
}

Everything is primitives: string, int, float, array.
Your domain concepts accidentally become “just data”.