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    <h3>Editing: AbstractSurrogate.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\HttpKernel\HttpCache;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;

/**
 * Abstract class implementing Surrogate capabilities to Request and Response instances.
 *
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 * @author Robin Chalas &lt;robin.chalas@gmail.com&gt;
 */
abstract class AbstractSurrogate implements SurrogateInterface
{
    protected $contentTypes;
    protected $phpEscapeMap = [
        ['&lt;?', '&lt;%', '&lt;s', '&lt;S'],
        ['&lt;?php echo &quot;&lt;?&quot;; ?&gt;', '&lt;?php echo &quot;&lt;%&quot;; ?&gt;', '&lt;?php echo &quot;&lt;s&quot;; ?&gt;', '&lt;?php echo &quot;&lt;S&quot;; ?&gt;'],
    ];

    /**
     * @param array $contentTypes An array of content-type that should be parsed for Surrogate information
     *                            (default: text/html, text/xml, application/xhtml+xml, and application/xml)
     */
    public function __construct(array $contentTypes = ['text/html', 'text/xml', 'application/xhtml+xml', 'application/xml'])
    {
        $this-&gt;contentTypes = $contentTypes;
    }

    /**
     * Returns a new cache strategy instance.
     */
    public function createCacheStrategy(): ResponseCacheStrategyInterface
    {
        return new ResponseCacheStrategy();
    }

    public function hasSurrogateCapability(Request $request): bool
    {
        if (null === $value = $request-&gt;headers-&gt;get('Surrogate-Capability')) {
            return false;
        }

        return str_contains($value, sprintf('%s/1.0', strtoupper($this-&gt;getName())));
    }

    public function addSurrogateCapability(Request $request)
    {
        $current = $request-&gt;headers-&gt;get('Surrogate-Capability');
        $new = sprintf('symfony=&quot;%s/1.0&quot;', strtoupper($this-&gt;getName()));

        $request-&gt;headers-&gt;set('Surrogate-Capability', $current ? $current.', '.$new : $new);
    }

    public function needsParsing(Response $response): bool
    {
        if (!$control = $response-&gt;headers-&gt;get('Surrogate-Control')) {
            return false;
        }

        $pattern = sprintf('#content=&quot;[^&quot;]*%s/1.0[^&quot;]*&quot;#', strtoupper($this-&gt;getName()));

        return (bool) preg_match($pattern, $control);
    }

    public function handle(HttpCache $cache, string $uri, string $alt, bool $ignoreErrors): string
    {
        $subRequest = Request::create($uri, Request::METHOD_GET, [], $cache-&gt;getRequest()-&gt;cookies-&gt;all(), [], $cache-&gt;getRequest()-&gt;server-&gt;all());

        try {
            $response = $cache-&gt;handle($subRequest, HttpKernelInterface::SUB_REQUEST, true);

            if (!$response-&gt;isSuccessful() &amp;&amp; Response::HTTP_NOT_MODIFIED !== $response-&gt;getStatusCode()) {
                throw new \RuntimeException(sprintf('Error when rendering &quot;%s&quot; (Status code is %d).', $subRequest-&gt;getUri(), $response-&gt;getStatusCode()));
            }

            return $response-&gt;getContent();
        } catch (\Exception $e) {
            if ($alt) {
                return $this-&gt;handle($cache, $alt, '', $ignoreErrors);
            }

            if (!$ignoreErrors) {
                throw $e;
            }
        }

        return '';
    }

    /**
     * Remove the Surrogate from the Surrogate-Control header.
     */
    protected function removeFromControl(Response $response)
    {
        if (!$response-&gt;headers-&gt;has('Surrogate-Control')) {
            return;
        }

        $value = $response-&gt;headers-&gt;get('Surrogate-Control');
        $upperName = strtoupper($this-&gt;getName());

        if (sprintf('content=&quot;%s/1.0&quot;', $upperName) == $value) {
            $response-&gt;headers-&gt;remove('Surrogate-Control');
        } elseif (preg_match(sprintf('#,\s*content=&quot;%s/1.0&quot;#', $upperName), $value)) {
            $response-&gt;headers-&gt;set('Surrogate-Control', preg_replace(sprintf('#,\s*content=&quot;%s/1.0&quot;#', $upperName), '', $value));
        } elseif (preg_match(sprintf('#content=&quot;%s/1.0&quot;,\s*#', $upperName), $value)) {
            $response-&gt;headers-&gt;set('Surrogate-Control', preg_replace(sprintf('#content=&quot;%s/1.0&quot;,\s*#', $upperName), '', $value));
        }
    }
}
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