<form method="POST">
    <h3>Editing: Esi.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;

/**
 * Esi implements the ESI capabilities to Request and Response instances.
 *
 * For more information, read the following W3C notes:
 *
 *  * ESI Language Specification 1.0 (http://www.w3.org/TR/esi-lang)
 *
 *  * Edge Architecture Specification (http://www.w3.org/TR/edge-arch)
 *
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 */
class Esi extends AbstractSurrogate
{
    public function getName()
    {
        return 'esi';
    }

    /**
     * {@inheritdoc}
     */
    public function addSurrogateControl(Response $response)
    {
        if (str_contains($response-&gt;getContent(), '&lt;esi:include')) {
            $response-&gt;headers-&gt;set('Surrogate-Control', 'content=&quot;ESI/1.0&quot;');
        }
    }

    /**
     * {@inheritdoc}
     */
    public function renderIncludeTag(string $uri, ?string $alt = null, bool $ignoreErrors = true, string $comment = '')
    {
        $html = sprintf('&lt;esi:include src=&quot;%s&quot;%s%s /&gt;',
            $uri,
            $ignoreErrors ? ' onerror=&quot;continue&quot;' : '',
            $alt ? sprintf(' alt=&quot;%s&quot;', $alt) : ''
        );

        if (!empty($comment)) {
            return sprintf(&quot;&lt;esi:comment text=\&quot;%s\&quot; /&gt;\n%s&quot;, $comment, $html);
        }

        return $html;
    }

    /**
     * {@inheritdoc}
     */
    public function process(Request $request, Response $response)
    {
        $type = $response-&gt;headers-&gt;get('Content-Type');
        if (empty($type)) {
            $type = 'text/html';
        }

        $parts = explode(';', $type);
        if (!\in_array($parts[0], $this-&gt;contentTypes)) {
            return $response;
        }

        // we don't use a proper XML parser here as we can have ESI tags in a plain text response
        $content = $response-&gt;getContent();
        $content = preg_replace('#&lt;esi\:remove&gt;.*?&lt;/esi\:remove&gt;#s', '', $content);
        $content = preg_replace('#&lt;esi\:comment[^&gt;]+&gt;#s', '', $content);

        $boundary = self::generateBodyEvalBoundary();
        $chunks = preg_split('#&lt;esi\:include\s+(.*?)\s*(?:/|&lt;/esi\:include)&gt;#', $content, -1, \PREG_SPLIT_DELIM_CAPTURE);

        $i = 1;
        while (isset($chunks[$i])) {
            $options = [];
            preg_match_all('/(src|onerror|alt)=&quot;([^&quot;]*?)&quot;/', $chunks[$i], $matches, \PREG_SET_ORDER);
            foreach ($matches as $set) {
                $options[$set[1]] = $set[2];
            }

            if (!isset($options['src'])) {
                throw new \RuntimeException('Unable to process an ESI tag without a &quot;src&quot; attribute.');
            }

            $chunks[$i] = $boundary.$options['src'].&quot;\n&quot;.($options['alt'] ?? '').&quot;\n&quot;.('continue' === ($options['onerror'] ?? '')).&quot;\n&quot;;
            $i += 2;
        }
        $content = $boundary.implode('', $chunks).$boundary;

        $response-&gt;setContent($content);
        $response-&gt;headers-&gt;set('X-Body-Eval', 'ESI');

        // remove ESI/1.0 from the Surrogate-Control header
        $this-&gt;removeFromControl($response);

        return $response;
    }
}
</textarea><br>
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