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   1  <?php
   2  
   3  /*
   4   * This file is part of the Symfony package.
   5   *
   6   * (c) Fabien Potencier <[email protected]>
   7   *
   8   * For the full copyright and license information, please view the LICENSE
   9   * file that was distributed with this source code.
  10   */
  11  
  12  namespace Symfony\Component\WebLink;
  13  
  14  use Psr\Link\LinkInterface;
  15  
  16  /**
  17   * Serializes a list of Link instances to an HTTP Link header.
  18   *
  19   * @see https://tools.ietf.org/html/rfc5988
  20   *
  21   * @author Kévin Dunglas <[email protected]>
  22   */
  23  final class HttpHeaderSerializer
  24  {
  25      /**
  26       * Builds the value of the "Link" HTTP header.
  27       *
  28       * @param LinkInterface[]|\Traversable $links
  29       */
  30      public function serialize(iterable $links): ?string
  31      {
  32          $elements = [];
  33          foreach ($links as $link) {
  34              if ($link->isTemplated()) {
  35                  continue;
  36              }
  37  
  38              $attributesParts = ['', sprintf('rel="%s"', implode(' ', $link->getRels()))];
  39              foreach ($link->getAttributes() as $key => $value) {
  40                  if (\is_array($value)) {
  41                      foreach ($value as $v) {
  42                          $attributesParts[] = sprintf('%s="%s"', $key, preg_replace('/(?<!\\\\)"/', '\"', $v));
  43                      }
  44  
  45                      continue;
  46                  }
  47  
  48                  if (!\is_bool($value)) {
  49                      $attributesParts[] = sprintf('%s="%s"', $key, preg_replace('/(?<!\\\\)"/', '\"', $value));
  50  
  51                      continue;
  52                  }
  53  
  54                  if (true === $value) {
  55                      $attributesParts[] = $key;
  56                  }
  57              }
  58  
  59              $elements[] = sprintf('<%s>%s', $link->getHref(), implode('; ', $attributesParts));
  60          }
  61  
  62          return $elements ? implode(',', $elements) : null;
  63      }
  64  }