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Html.php
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<?php
namespace Drupal\Component\Utility;
use Masterminds\HTML5;
use Masterminds\HTML5\Serializer\Traverser;
/**
* Provides DOMDocument helpers for parsing and serializing HTML strings.
*
* @ingroup utility
*/
class Html {
/**
* An array of previously cleaned HTML classes.
*
* @var array
*/
protected static $classes = [];
/**
* An array of the initial IDs used in one request.
*
* @var array
*/
protected static $seenIdsInit;
/**
* An array of IDs, including incremented versions when an ID is duplicated.
*
* @var array
*/
protected static $seenIds;
/**
* Stores whether the current request was sent via AJAX.
*
* @var bool
*/
protected static $isAjax = FALSE;
/**
* All attributes that may contain URIs.
*
* - The attributes 'code' and 'codebase' are omitted, because they only exist
* for the <applet> tag. The time of Java applets has passed.
* - The attribute 'icon' is omitted, because no browser implements the
* <command> tag anymore.
* See https://developer.mozilla.org/en-US/docs/Web/HTML/Element/command.
* - The 'manifest' attribute is omitted because it only exists for the <html>
* tag. That tag only makes sense in an HTML-served-as-HTML context, in
* which case relative URLs are guaranteed to work.
*
* @var string[]
*
* @see https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes
* @see https://stackoverflow.com/questions/2725156/complete-list-of-html-tag-attributes-which-have-a-url-value
*/
protected static $uriAttributes = ['href', 'poster', 'src', 'cite', 'data', 'action', 'formaction', 'srcset', 'about'];
/**
* Prepares a string for use as a valid class name.
*
* Do not pass one string containing multiple classes as they will be
* incorrectly concatenated with dashes, i.e. "one two" will become "one-two".
*
* @param mixed $class
* The class name to clean. It can be a string or anything that can be cast
* to string.
*
* @return string
* The cleaned class name.
*/
public static function getClass($class) {
$class = (string) $class;
if (!isset(static::$classes[$class])) {
static::$classes[$class] = static::cleanCssIdentifier(mb_strtolower($class));
}
return static::$classes[$class];
}
/**
* Prepares a string for use as a CSS identifier (element, class, or ID name).
*
* Link below shows the syntax for valid CSS identifiers (including element
* names, classes, and IDs in selectors).
*
* @param string $identifier
* The identifier to clean.
* @param array $filter
* An array of string replacements to use on the identifier.
*
* @return string
* The cleaned identifier.
*
* @see https://www.w3.org/TR/CSS21/syndata.html#characters
*/
public static function cleanCssIdentifier(
$identifier,
array $filter = [
' ' => '-',
'_' => '-',
'/' => '-',
'[' => '-',
']' => '',
],
) {
// We could also use strtr() here but its much slower than str_replace(). In
// order to keep '__' to stay '__' we first replace it with a different
// placeholder after checking that it is not defined as a filter.
$double_underscore_replacements = 0;
if (!isset($filter['__'])) {
$identifier = str_replace('__', '##', $identifier, $double_underscore_replacements);
}
$identifier = str_replace(array_keys($filter), array_values($filter), $identifier);
// Replace temporary placeholder '##' with '__' only if the original
// $identifier contained '__'.
if ($double_underscore_replacements > 0) {
$identifier = str_replace('##', '__', $identifier);
}
// Valid characters in a CSS identifier are:
// - the hyphen (U+002D)
// - a-z (U+0030 - U+0039)
// - A-Z (U+0041 - U+005A)
// - the underscore (U+005F)
// - 0-9 (U+0061 - U+007A)
// - ISO 10646 characters U+00A1 and higher
// We strip out any character not in the above list.
$identifier = preg_replace('/[^\x{002D}\x{0030}-\x{0039}\x{0041}-\x{005A}\x{005F}\x{0061}-\x{007A}\x{00A1}-\x{FFFF}]/u', '', $identifier);
// Identifiers cannot start with a digit, two hyphens, or a hyphen followed
// by a digit.
$identifier = preg_replace([
'/^[0-9]/',
'/^(-[0-9])|^(--)/',
], ['_', '__'], $identifier);
return $identifier;
}
/**
* Sets if this request is an Ajax request.
*
* @param bool $is_ajax
* TRUE if this request is an Ajax request, FALSE otherwise.
*/
public static function setIsAjax($is_ajax) {
static::$isAjax = $is_ajax;
}
/**
* Prepares a string for use as a valid HTML ID and guarantees uniqueness.
*
* This function ensures that each passed HTML ID value only exists once on
* the page. By tracking the already returned ids, this function enables
* forms, blocks, and other content to be output multiple times on the same
* page, without breaking HTML validation.
*
* For already existing IDs, a counter is appended to the ID string.
* Therefore, JavaScript and CSS code should not rely on any value that was
* generated by this function and instead should rely on manually added CSS
* classes or similarly reliable constructs.
*
* Two consecutive hyphens separate the counter from the original ID. To
* manage uniqueness across multiple Ajax requests on the same page, Ajax
* requests POST an array of all IDs currently present on the page, which are
* used to prime this function's cache upon first invocation.
*
* To allow reverse-parsing of IDs submitted via Ajax, any multiple
* consecutive hyphens in the originally passed $id are replaced with a
* single hyphen.
*
* @param string $id
* The ID to clean.
*
* @return string
* The cleaned ID.
*/
public static function getUniqueId($id) {
// If this is an Ajax request, then content returned by this page request
// will be merged with content already on the base page. The HTML IDs must
// be unique for the fully merged content. Therefore use unique IDs.
if (static::$isAjax) {
return static::getId($id) . '--' . Crypt::randomBytesBase64(8);
}
// @todo Remove all that code once we switch over to random IDs only,
// see https://www.drupal.org/node/1090592.
if (!isset(static::$seenIdsInit)) {
static::$seenIdsInit = [];
}
if (!isset(static::$seenIds)) {
static::$seenIds = static::$seenIdsInit;
}
$id = static::getId($id);
// Ensure IDs are unique by appending a counter after the first occurrence.
// The counter needs to be appended with a delimiter that does not exist in
// the base ID. Requiring a unique delimiter helps ensure that we really do
// return unique IDs and also helps us re-create the $seen_ids array during
// Ajax requests.
if (isset(static::$seenIds[$id])) {
$id = $id . '--' . ++static::$seenIds[$id];
}
else {
static::$seenIds[$id] = 1;
}
return $id;
}
/**
* Prepares a string for use as a valid HTML ID.
*
* Only use this function when you want to intentionally skip the uniqueness
* guarantee of self::getUniqueId().
*
* @param string $id
* The ID to clean.
*
* @return string
* The cleaned ID.
*
* @see self::getUniqueId()
*/
public static function getId($id) {
$id = str_replace([' ', '_', '[', ']'], ['-', '-', '-', ''], mb_strtolower($id));
// As defined in https://www.w3.org/TR/html4/types.html#type-name, HTML IDs
// can only contain letters, digits ([0-9]), hyphens ("-"), underscores
// ("_"), colons (":"), and periods ("."). We strip out any character not in
// that list. Note that the CSS spec doesn't allow colons or periods in
// identifiers (https://www.w3.org/TR/CSS21/syndata.html#characters), so we
// strip those two characters as well.
$id = preg_replace('/[^A-Za-z0-9\-_]/', '', $id);
// Removing multiple consecutive hyphens.
$id = preg_replace('/\-+/', '-', $id);
return $id;
}
/**
* Resets the list of seen IDs.
*/
public static function resetSeenIds() {
static::$seenIds = NULL;
}
/**
* Normalizes an HTML snippet.
*
* This function is essentially \DOMDocument::normalizeDocument(), but
* operates on an HTML string instead of a \DOMDocument.
*
* @param string $html
* The HTML string to normalize.
*
* @return string
* The normalized HTML string.
*/
public static function normalize($html) {
$document = static::load($html);
return static::serialize($document);
}
/**
* Parses an HTML snippet and returns it as a DOM object.
*
* This function loads the body part of a partial HTML document and returns a
* full \DOMDocument object that represents this document.
*
* Use \Drupal\Component\Utility\Html::serialize() to serialize this
* \DOMDocument back to a string.
*
* @param string $html
* The partial HTML snippet to load. Invalid markup will be corrected on
* import.
*
* @return \DOMDocument
* A \DOMDocument that represents the loaded HTML snippet.
*/
public static function load($html) {
// Instantiate the HTML5 parser, but without the HTML5 namespace being
// added to the DOM document.
$html5 = new HTML5(['disable_html_ns' => TRUE, 'encoding' => 'UTF-8']);
// Attach the provided HTML inside the body. Rely on the HTML5 parser to
// close the body tag.
return $html5->loadHTML('<body>' . $html);
}
/**
* Converts the body of a \DOMDocument back to an HTML snippet.
*
* The function serializes the body part of a \DOMDocument back to an HTML
* snippet. The resulting HTML snippet will be properly formatted to be
* compatible with HTML user agents.
*
* @param \DOMDocument $document
* A \DOMDocument object to serialize, only the tags below the first <body>
* node will be converted.
*
* @return string
* A valid HTML snippet, as a string.
*/
public static function serialize(\DOMDocument $document) {
$body_node = $document->getElementsByTagName('body')->item(0);
$html = '';
if ($body_node !== NULL) {
foreach ($body_node->getElementsByTagName('script') as $node) {
static::escapeCdataElement($node);
}
foreach ($body_node->getElementsByTagName('style') as $node) {
static::escapeCdataElement($node, '/*', '*/');
}
// Serialize the body using our custom set of rules.
// @see \Masterminds\HTML5::saveHTML()
$stream = fopen('php://temp', 'wb');
$rules = new HtmlSerializerRules($stream);
foreach ($body_node->childNodes as $node) {
$traverser = new Traverser($node, $stream, $rules);
$traverser->walk();
}
$rules->unsetTraverser();
$html = stream_get_contents($stream, -1, 0);
fclose($stream);
}
// Normalize all newlines.
$html = str_replace(["\r\n", "\r"], "\n", $html);
return $html;
}
/**
* Adds comments around a <!CDATA section in a \DOMNode.
*
* \DOMDocument::loadHTML() in \Drupal\Component\Utility\Html::load() makes
* CDATA sections from the contents of inline script and style tags. This can
* cause HTML4 browsers to throw exceptions.
*
* This function attempts to solve the problem by creating a
* \DOMDocumentFragment to comment the CDATA tag.
*
* @param \DOMNode $node
* The element potentially containing a CDATA node.
* @param string $comment_start
* (optional) A string to use as a comment start marker to escape the CDATA
* declaration. Defaults to '//'.
* @param string $comment_end
* (optional) A string to use as a comment end marker to escape the CDATA
* declaration. Defaults to an empty string.
*/
public static function escapeCdataElement(\DOMNode $node, $comment_start = '//', $comment_end = '') {
foreach ($node->childNodes as $child_node) {
if ($child_node instanceof \DOMCdataSection) {
$data = $child_node->data;
if (!str_contains($child_node->data, 'CDATA')) {
$embed_prefix = "\n{$comment_start}<![CDATA[{$comment_end}\n";
$embed_suffix = "\n{$comment_start}]]>{$comment_end}\n";
$data = $embed_prefix . $data . $embed_suffix;
}
$fragment = $node->ownerDocument->createDocumentFragment();
$fragment->appendXML($data);
$node->appendChild($fragment);
$node->removeChild($child_node);
}
}
}
/**
* Decodes all HTML entities including numerical ones to regular UTF-8 bytes.
*
* Double-escaped entities will only be decoded once ("&lt;" becomes
* "<", not "<"). Be careful when using this function, as it will revert
* previous sanitization efforts (<script> will become <script>).
*
* This method is not the opposite of Html::escape(). For example, this method
* will convert "é" to "é", whereas Html::escape() will not convert "é"
* to "é".
*
* @param string $text
* The text to decode entities in.
*
* @return string
* The input $text, with all HTML entities decoded once.
*
* @see html_entity_decode()
* @see \Drupal\Component\Utility\Html::escape()
*/
public static function decodeEntities(string $text): string {
return html_entity_decode($text, ENT_QUOTES, 'UTF-8');
}
/**
* Escapes text by converting special characters to HTML entities.
*
* This method escapes HTML for sanitization purposes by replacing the
* following special characters with their HTML entity equivalents:
* - & (ampersand) becomes &
* - " (double quote) becomes "
* - ' (single quote) becomes '
* - < (less than) becomes <
* - > (greater than) becomes >
* Special characters that have already been escaped will be double-escaped
* (for example, "<" becomes "&lt;"), and invalid UTF-8 encoding
* will be converted to the Unicode replacement character ("�").
*
* This method is not the opposite of Html::decodeEntities(). For example,
* this method will not encode "é" to "é", whereas
* Html::decodeEntities() will convert all HTML entities to UTF-8 bytes,
* including "é" and "<" to "é" and "<".
*
* When constructing @link theme_render render arrays @endlink passing the
* output of Html::escape() to '#markup' is not recommended. Use the
* '#plain_text' key instead and the renderer will autoescape the text.
*
* @param string $text
* The input text.
*
* @return string
* The text with all HTML special characters converted.
*
* @see htmlspecialchars()
* @see \Drupal\Component\Utility\Html::decodeEntities()
*
* @ingroup sanitization
*/
public static function escape(string $text): string {
return htmlspecialchars($text, ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8');
}
/**
* 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 'https://example.com/some-article') or from
* a listing or feed (for example 'https://example.com/all-articles') their
* "current path" differs, resulting in different absolute URLs:
* 'https://example.com/some-article/image.png' versus
* 'https://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.
*
* @param string $html
* The partial HTML snippet to load. Invalid markup will be corrected on
* import.
* @param string $scheme_and_host
* The root URL, which has a URI scheme, host and optional port.
*
* @return string
* The updated HTML snippet.
*/
public static function transformRootRelativeUrlsToAbsolute($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);
}
}