Validator interface

composer require quillstack/validator-interface

PackagistSource PHP ^8.1

Common interface for Validator classes.

One method, and two exception interfaces. Something which validates says so by implementing this, and something which fails validation says so by implementing the other — so a caller can tell a value it does not like from a mistake in the code.

Requirements

• PHP 8.1 or newer

Installation

composer require quillstack/validator-interface

Usage

use Quillstack\ValidatorInterface\ValidatorInterface;

final class HostValidator implements ValidatorInterface
{
    public function __construct(private readonly string $host)
    {
    }

    public function validate(): bool
    {
        if (filter_var($this->host, FILTER_VALIDATE_DOMAIN) === false) {
            throw new UnknownHostException("Not a host: {$this->host}");
        }

        return true;
    }
}

The exception says which kind of thing went wrong:

use Quillstack\ValidatorInterface\ValidationExceptionInterface;

final class UnknownHostException extends UriException implements ValidationExceptionInterface
{
}

Catching it is then catching one thing:

try {
    $validator->validate();
} catch (ValidationExceptionInterface $exception) {
    // What was given is wrong — not the code that was given it.
}

Technical documentation

Interface	What it means
ValidatorInterface	validate(): bool — the thing validates something
ValidatorExceptionInterface	something went wrong in a validator
ValidationExceptionInterface	the value was wrong, which is the usual case; extends the one above

validate() answers true or throws. It does not answer false: a caller which ignores the answer would carry on with a value nobody accepted, and a thrown exception cannot be ignored by accident.

Who implements it

• quillstack/uri — the scheme and the host of a URI
• quillstack/server-request — what $_SERVER must hold
• quillstack/response — that a status code is one that exists

There is nothing to run here: a package which only names things has no behaviour to test.

License

MIT. See LICENSE.