public static function Html::transformRootRelativeUrlsToAbsolute

Converts all root-relative URLs to absolute URLs.

Does not change any existing protocol-relative or absolute URLs. Does not change other relative URLs because they would result in different absolute URLs depending on the current path. For example: when the same content containing such a relative URL (for example 'image.png'), is served from its canonical URL (for example 'http://example.com/some-article') or from a listing or feed (for example 'http://example.com/all-articles') their "current path" differs, resulting in different absolute URLs: 'http://example.com/some-article/image.png' versus 'http://example.com/all-articles/image.png'. Only one can be correct. Therefore relative URLs that are not root-relative cannot be safely transformed and should generally be avoided.

Necessary for HTML that is served outside of a website, for example, RSS and email.

Parameters

string $html: The partial HTML snippet to load. Invalid markup will be corrected on import.

string $scheme_and_host: The root URL, which has a URI scheme, host and optional port.

Return value

string The updated HTML snippet.

File

core/lib/Drupal/Component/Utility/Html.php, line 467

Class

Html

Provides DOMDocument helpers for parsing and serializing HTML strings.

Namespace

Code

public static function transformRootRelativeUrlsToAbsolute($html, $scheme_and_host) {
  assert(empty(array_diff(array_keys(parse_url($scheme_and_host)), [
    "scheme",
    "host",
    "port",
  ])), '$scheme_and_host contains scheme, host and port at most.');
  assert(isset(parse_url($scheme_and_host)["scheme"]), '$scheme_and_host is absolute and hence has a scheme.');
  assert(isset(parse_url($scheme_and_host)["host"]), '$base_url is absolute and hence has a host.');
  $html_dom = Html::load($html);
  $xpath = new \DOMXpath($html_dom);

  // Update all root-relative URLs to absolute URLs in the given HTML.
  // Perform on attributes that may contain a single URI.
  foreach (static::$uriAttributes as $attr) {
    foreach ($xpath
      ->query("//*[starts-with(@{$attr}, '/') and not(starts-with(@{$attr}, '//'))]") as $node) {
      $node
        ->setAttribute($attr, $scheme_and_host . $node
        ->getAttribute($attr));
    }
  }

  // Perform on each URI within "srcset" attributes.
  foreach ($xpath
    ->query("//*[@srcset]") as $node) {

    // @see https://html.spec.whatwg.org/multipage/embedded-content.html#attr-img-srcset
    // @see https://html.spec.whatwg.org/multipage/embedded-content.html#image-candidate-string
    $image_candidate_strings = explode(',', $node
      ->getAttribute('srcset'));
    $image_candidate_strings = array_filter(array_map('trim', $image_candidate_strings));
    foreach ($image_candidate_strings as $key => $image_candidate_string) {
      if ($image_candidate_string[0] === '/' && $image_candidate_string[1] !== '/') {
        $image_candidate_strings[$key] = $scheme_and_host . $image_candidate_string;
      }
    }
    $node
      ->setAttribute('srcset', implode(', ', $image_candidate_strings));
  }
  return Html::serialize($html_dom);
}