235 lines
8.9 KiB
PHP
235 lines
8.9 KiB
PHP
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<?php
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/*
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* This file is part of the Symfony package.
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*
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* (c) Fabien Potencier <fabien@symfony.com>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Symfony\Component\HttpKernel\HttpCache;
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use Symfony\Component\HttpFoundation\Response;
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/**
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* ResponseCacheStrategy knows how to compute the Response cache HTTP header
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* based on the different response cache headers.
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*
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* This implementation changes the main response TTL to the smallest TTL received
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* or force validation if one of the surrogates has validation cache strategy.
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*
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* @author Fabien Potencier <fabien@symfony.com>
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*/
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class ResponseCacheStrategy implements ResponseCacheStrategyInterface
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{
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/**
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* Cache-Control headers that are sent to the final response if they appear in ANY of the responses.
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*/
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private const OVERRIDE_DIRECTIVES = ['private', 'no-cache', 'no-store', 'no-transform', 'must-revalidate', 'proxy-revalidate'];
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/**
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* Cache-Control headers that are sent to the final response if they appear in ALL of the responses.
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*/
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private const INHERIT_DIRECTIVES = ['public', 'immutable'];
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private $embeddedResponses = 0;
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private $isNotCacheableResponseEmbedded = false;
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private $age = 0;
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private $flagDirectives = [
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'no-cache' => null,
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'no-store' => null,
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'no-transform' => null,
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'must-revalidate' => null,
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'proxy-revalidate' => null,
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'public' => null,
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'private' => null,
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'immutable' => null,
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];
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private $ageDirectives = [
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'max-age' => null,
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's-maxage' => null,
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'expires' => null,
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];
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/**
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* {@inheritdoc}
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*/
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public function add(Response $response)
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{
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++$this->embeddedResponses;
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foreach (self::OVERRIDE_DIRECTIVES as $directive) {
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if ($response->headers->hasCacheControlDirective($directive)) {
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$this->flagDirectives[$directive] = true;
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}
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}
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foreach (self::INHERIT_DIRECTIVES as $directive) {
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if (false !== $this->flagDirectives[$directive]) {
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$this->flagDirectives[$directive] = $response->headers->hasCacheControlDirective($directive);
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}
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}
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$age = $response->getAge();
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$this->age = max($this->age, $age);
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if ($this->willMakeFinalResponseUncacheable($response)) {
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$this->isNotCacheableResponseEmbedded = true;
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return;
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}
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$isHeuristicallyCacheable = $response->headers->hasCacheControlDirective('public');
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$maxAge = $response->headers->hasCacheControlDirective('max-age') ? (int) $response->headers->getCacheControlDirective('max-age') : null;
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$this->storeRelativeAgeDirective('max-age', $maxAge, $age, $isHeuristicallyCacheable);
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$sharedMaxAge = $response->headers->hasCacheControlDirective('s-maxage') ? (int) $response->headers->getCacheControlDirective('s-maxage') : $maxAge;
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$this->storeRelativeAgeDirective('s-maxage', $sharedMaxAge, $age, $isHeuristicallyCacheable);
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$expires = $response->getExpires();
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$expires = null !== $expires ? (int) $expires->format('U') - (int) $response->getDate()->format('U') : null;
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$this->storeRelativeAgeDirective('expires', $expires >= 0 ? $expires : null, 0, $isHeuristicallyCacheable);
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}
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/**
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* {@inheritdoc}
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*/
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public function update(Response $response)
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{
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// if we have no embedded Response, do nothing
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if (0 === $this->embeddedResponses) {
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return;
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}
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// Remove validation related headers of the master response,
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// because some of the response content comes from at least
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// one embedded response (which likely has a different caching strategy).
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$response->setEtag(null);
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$response->setLastModified(null);
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$this->add($response);
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$response->headers->set('Age', $this->age);
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if ($this->isNotCacheableResponseEmbedded) {
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if ($this->flagDirectives['no-store']) {
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$response->headers->set('Cache-Control', 'no-cache, no-store, must-revalidate');
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} else {
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$response->headers->set('Cache-Control', 'no-cache, must-revalidate');
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}
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return;
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}
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$flags = array_filter($this->flagDirectives);
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if (isset($flags['must-revalidate'])) {
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$flags['no-cache'] = true;
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}
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$response->headers->set('Cache-Control', implode(', ', array_keys($flags)));
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$maxAge = null;
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if (is_numeric($this->ageDirectives['max-age'])) {
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$maxAge = $this->ageDirectives['max-age'] + $this->age;
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$response->headers->addCacheControlDirective('max-age', $maxAge);
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}
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if (is_numeric($this->ageDirectives['s-maxage'])) {
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$sMaxage = $this->ageDirectives['s-maxage'] + $this->age;
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if ($maxAge !== $sMaxage) {
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$response->headers->addCacheControlDirective('s-maxage', $sMaxage);
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}
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}
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if (is_numeric($this->ageDirectives['expires'])) {
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$date = clone $response->getDate();
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$date->modify('+'.($this->ageDirectives['expires'] + $this->age).' seconds');
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$response->setExpires($date);
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}
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}
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/**
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* RFC2616, Section 13.4.
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*
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* @see https://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.4
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*/
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private function willMakeFinalResponseUncacheable(Response $response): bool
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{
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// RFC2616: A response received with a status code of 200, 203, 300, 301 or 410
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// MAY be stored by a cache […] unless a cache-control directive prohibits caching.
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if ($response->headers->hasCacheControlDirective('no-cache')
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|| $response->headers->getCacheControlDirective('no-store')
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) {
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return true;
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}
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// Last-Modified and Etag headers cannot be merged, they render the response uncacheable
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// by default (except if the response also has max-age etc.).
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if (\in_array($response->getStatusCode(), [200, 203, 300, 301, 410])
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&& null === $response->getLastModified()
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&& null === $response->getEtag()
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) {
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return false;
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}
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// RFC2616: A response received with any other status code (e.g. status codes 302 and 307)
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// MUST NOT be returned in a reply to a subsequent request unless there are
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// cache-control directives or another header(s) that explicitly allow it.
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$cacheControl = ['max-age', 's-maxage', 'must-revalidate', 'proxy-revalidate', 'public', 'private'];
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foreach ($cacheControl as $key) {
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if ($response->headers->hasCacheControlDirective($key)) {
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return false;
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}
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}
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if ($response->headers->has('Expires')) {
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return false;
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}
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return true;
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}
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/**
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* Store lowest max-age/s-maxage/expires for the final response.
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*
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* The response might have been stored in cache a while ago. To keep things comparable,
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* we have to subtract the age so that the value is normalized for an age of 0.
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*
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* If the value is lower than the currently stored value, we update the value, to keep a rolling
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* minimal value of each instruction.
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*
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* If the value is NULL and the isHeuristicallyCacheable parameter is false, the directive will
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* not be set on the final response. In this case, not all responses had the directive set and no
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* value can be found that satisfies the requirements of all responses. The directive will be dropped
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* from the final response.
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*
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* If the isHeuristicallyCacheable parameter is true, however, the current response has been marked
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* as cacheable in a public (shared) cache, but did not provide an explicit lifetime that would serve
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* as an upper bound. In this case, we can proceed and possibly keep the directive on the final response.
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*/
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private function storeRelativeAgeDirective(string $directive, ?int $value, int $age, bool $isHeuristicallyCacheable)
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{
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if (null === $value) {
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if ($isHeuristicallyCacheable) {
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/*
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* See https://datatracker.ietf.org/doc/html/rfc7234#section-4.2.2
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* This particular response does not require maximum lifetime; heuristics might be applied.
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* Other responses, however, might have more stringent requirements on maximum lifetime.
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* So, return early here so that the final response can have the more limiting value set.
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*/
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return;
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}
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$this->ageDirectives[$directive] = false;
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}
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if (false !== $this->ageDirectives[$directive]) {
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$value -= $age;
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$this->ageDirectives[$directive] = null !== $this->ageDirectives[$directive] ? min($this->ageDirectives[$directive], $value) : $value;
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}
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}
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}
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