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    <h3>Editing: ResponseHeaderBag.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\HttpFoundation;

/**
 * ResponseHeaderBag is a container for Response HTTP headers.
 *
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 */
class ResponseHeaderBag extends HeaderBag
{
    public const COOKIES_FLAT = 'flat';
    public const COOKIES_ARRAY = 'array';

    public const DISPOSITION_ATTACHMENT = 'attachment';
    public const DISPOSITION_INLINE = 'inline';

    protected $computedCacheControl = [];
    protected $cookies = [];
    protected $headerNames = [];

    public function __construct(array $headers = [])
    {
        parent::__construct($headers);

        if (!isset($this-&gt;headers['cache-control'])) {
            $this-&gt;set('Cache-Control', '');
        }

        /* RFC2616 - 14.18 says all Responses need to have a Date */
        if (!isset($this-&gt;headers['date'])) {
            $this-&gt;initDate();
        }
    }

    /**
     * Returns the headers, with original capitalizations.
     *
     * @return array
     */
    public function allPreserveCase()
    {
        $headers = [];
        foreach ($this-&gt;all() as $name =&gt; $value) {
            $headers[$this-&gt;headerNames[$name] ?? $name] = $value;
        }

        return $headers;
    }

    public function allPreserveCaseWithoutCookies()
    {
        $headers = $this-&gt;allPreserveCase();
        if (isset($this-&gt;headerNames['set-cookie'])) {
            unset($headers[$this-&gt;headerNames['set-cookie']]);
        }

        return $headers;
    }

    /**
     * {@inheritdoc}
     */
    public function replace(array $headers = [])
    {
        $this-&gt;headerNames = [];

        parent::replace($headers);

        if (!isset($this-&gt;headers['cache-control'])) {
            $this-&gt;set('Cache-Control', '');
        }

        if (!isset($this-&gt;headers['date'])) {
            $this-&gt;initDate();
        }
    }

    /**
     * {@inheritdoc}
     */
    public function all(?string $key = null)
    {
        $headers = parent::all();

        if (null !== $key) {
            $key = strtr($key, self::UPPER, self::LOWER);

            return 'set-cookie' !== $key ? $headers[$key] ?? [] : array_map('strval', $this-&gt;getCookies());
        }

        foreach ($this-&gt;getCookies() as $cookie) {
            $headers['set-cookie'][] = (string) $cookie;
        }

        return $headers;
    }

    /**
     * {@inheritdoc}
     */
    public function set(string $key, $values, bool $replace = true)
    {
        $uniqueKey = strtr($key, self::UPPER, self::LOWER);

        if ('set-cookie' === $uniqueKey) {
            if ($replace) {
                $this-&gt;cookies = [];
            }
            foreach ((array) $values as $cookie) {
                $this-&gt;setCookie(Cookie::fromString($cookie));
            }
            $this-&gt;headerNames[$uniqueKey] = $key;

            return;
        }

        $this-&gt;headerNames[$uniqueKey] = $key;

        parent::set($key, $values, $replace);

        // ensure the cache-control header has sensible defaults
        if (\in_array($uniqueKey, ['cache-control', 'etag', 'last-modified', 'expires'], true) &amp;&amp; '' !== $computed = $this-&gt;computeCacheControlValue()) {
            $this-&gt;headers['cache-control'] = [$computed];
            $this-&gt;headerNames['cache-control'] = 'Cache-Control';
            $this-&gt;computedCacheControl = $this-&gt;parseCacheControl($computed);
        }
    }

    /**
     * {@inheritdoc}
     */
    public function remove(string $key)
    {
        $uniqueKey = strtr($key, self::UPPER, self::LOWER);
        unset($this-&gt;headerNames[$uniqueKey]);

        if ('set-cookie' === $uniqueKey) {
            $this-&gt;cookies = [];

            return;
        }

        parent::remove($key);

        if ('cache-control' === $uniqueKey) {
            $this-&gt;computedCacheControl = [];
        }

        if ('date' === $uniqueKey) {
            $this-&gt;initDate();
        }
    }

    /**
     * {@inheritdoc}
     */
    public function hasCacheControlDirective(string $key)
    {
        return \array_key_exists($key, $this-&gt;computedCacheControl);
    }

    /**
     * {@inheritdoc}
     */
    public function getCacheControlDirective(string $key)
    {
        return $this-&gt;computedCacheControl[$key] ?? null;
    }

    public function setCookie(Cookie $cookie)
    {
        $this-&gt;cookies[$cookie-&gt;getDomain()][$cookie-&gt;getPath()][$cookie-&gt;getName()] = $cookie;
        $this-&gt;headerNames['set-cookie'] = 'Set-Cookie';
    }

    /**
     * Removes a cookie from the array, but does not unset it in the browser.
     */
    public function removeCookie(string $name, ?string $path = '/', ?string $domain = null)
    {
        if (null === $path) {
            $path = '/';
        }

        unset($this-&gt;cookies[$domain][$path][$name]);

        if (empty($this-&gt;cookies[$domain][$path])) {
            unset($this-&gt;cookies[$domain][$path]);

            if (empty($this-&gt;cookies[$domain])) {
                unset($this-&gt;cookies[$domain]);
            }
        }

        if (empty($this-&gt;cookies)) {
            unset($this-&gt;headerNames['set-cookie']);
        }
    }

    /**
     * Returns an array with all cookies.
     *
     * @return Cookie[]
     *
     * @throws \InvalidArgumentException When the $format is invalid
     */
    public function getCookies(string $format = self::COOKIES_FLAT)
    {
        if (!\in_array($format, [self::COOKIES_FLAT, self::COOKIES_ARRAY])) {
            throw new \InvalidArgumentException(sprintf('Format &quot;%s&quot; invalid (%s).', $format, implode(', ', [self::COOKIES_FLAT, self::COOKIES_ARRAY])));
        }

        if (self::COOKIES_ARRAY === $format) {
            return $this-&gt;cookies;
        }

        $flattenedCookies = [];
        foreach ($this-&gt;cookies as $path) {
            foreach ($path as $cookies) {
                foreach ($cookies as $cookie) {
                    $flattenedCookies[] = $cookie;
                }
            }
        }

        return $flattenedCookies;
    }

    /**
     * Clears a cookie in the browser.
     */
    public function clearCookie(string $name, ?string $path = '/', ?string $domain = null, bool $secure = false, bool $httpOnly = true, ?string $sameSite = null)
    {
        $this-&gt;setCookie(new Cookie($name, null, 1, $path, $domain, $secure, $httpOnly, false, $sameSite));
    }

    /**
     * @see HeaderUtils::makeDisposition()
     */
    public function makeDisposition(string $disposition, string $filename, string $filenameFallback = '')
    {
        return HeaderUtils::makeDisposition($disposition, $filename, $filenameFallback);
    }

    /**
     * Returns the calculated value of the cache-control header.
     *
     * This considers several other headers and calculates or modifies the
     * cache-control header to a sensible, conservative value.
     *
     * @return string
     */
    protected function computeCacheControlValue()
    {
        if (!$this-&gt;cacheControl) {
            if ($this-&gt;has('Last-Modified') || $this-&gt;has('Expires')) {
                return 'private, must-revalidate'; // allows for heuristic expiration (RFC 7234 Section 4.2.2) in the case of &quot;Last-Modified&quot;
            }

            // conservative by default
            return 'no-cache, private';
        }

        $header = $this-&gt;getCacheControlHeader();
        if (isset($this-&gt;cacheControl['public']) || isset($this-&gt;cacheControl['private'])) {
            return $header;
        }

        // public if s-maxage is defined, private otherwise
        if (!isset($this-&gt;cacheControl['s-maxage'])) {
            return $header.', private';
        }

        return $header;
    }

    private function initDate(): void
    {
        $this-&gt;set('Date', gmdate('D, d M Y H:i:s').' GMT');
    }
}
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