URL resolver for HTML

A simple library which resolves relative URLs in HTML DOM trees

Features

• Supports both DOMDocument and Dom\Document trees (since PHP 8.4)
• Handles all URL-bearing attributes in HTML, SVG, and MathML, including whitespace-separated URL-list attributes and srcset attributes
• Honours HTML <base> elements in HTML documents

Requirements

• PHP 7.1 or later
• The dom extension
• The mensbeam/uri library or other polyfill for the uri extension if using PHP versions prior to 8.5

Usage

Currently the library consists of a single static method, which will query a DOM tree for URL-bearing attributes starting from a context node (a document, element, or document fragment) and modify the tree in-place.

namespace MensBeam\HTML;

class UrlResolver {
    public static function resolveTree(\DOMDocument|\DOMElement|\DOMDocumentFragment|\Dom\Document|\Dom\Element|\Dom\DocumentFragment $node, \Uri\WhatWg\Url|string $baseUrl): void;
}

The $baseUrl argument must be an absolute URL; an exception will be thrown otherwise.

Notes

• Since the process of resolution also involves some measure of normalization, absolute URLs already present in the document may not be identical after the resolution process
• The presence of an (X)HTML <base> element with a relative URL in a non-HTML document (such as an SVG document) may yield unintuitive results as to that element's resolved URL; the element itself will not be factored into the base URL, however
• The xml:base attribute is neither factored into URL resolution, nor modified during processing
• HTML defines some attributes as containing non-empty URLs; if these attributes are in fact empty they are left unchanged during processing