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AcceptLanguageNegotiator

Negotiates the Accept-Language request header (RFC 7231 §5.3.5) against a list of supported locales.

<?php

use Chubbyphp\Negotiation\AcceptLanguageNegotiator;
use Psr\Http\Message\ServerRequestInterface;

/** @var ServerRequestInterface $request */
$request = $request->withHeader('Accept-Language', 'de,en-US;q=0.7,en;q=0.3');

$negotiator = new AcceptLanguageNegotiator(['en', 'de']);

$value = $negotiator->negotiate($request); // NegotiatedValue|null
$value->getValue();                        // 'de'
$value->getAttributes();                   // ['q' => '1.0']

$negotiator->getSupportedLocales();        // ['en', 'de']

Matching rules

The header is split into locales, each with its parameters (a missing q counts as 1.0), and sorted by q descending. The first rule that produces a match wins:

# Rule Header (sorted by q) Supported Result
1 exact locale de,en;q=0.3 ['en', 'de'] de (q=1.0)
2 language of a regional locale de-CH ['de'] de (q=1.0)
3 wildcard * → first supported locale en-US;q=0.7,*;q=0.3 ['de'] de (q=0.3)

Rule 2 only strips a single region (de-CH → de); de-DE-AT does not match de. The fallback is one-directional: a requested de does not match a supported de-CH.

Returns null when

  • the list of supported locales is empty
  • the request has no Accept-Language header
  • no rule above produces a match