make-youtube-accessible-embed.php

<?php
/**
 * Make YouTube Accessible Embed Plugin
 *
 * @package   TBK_YouTube_Embed_Mods
 * @author    Weston Ruter
 * @link      https://gist.github.com/westonruter/8199d0fcb417a909380b0aeff4247cf7
 * @license   GPL-2.0-or-later
 * @copyright 2023 Google Inc.
 *
 * @wordpress-plugin
 * Plugin Name: Make YouTube Accessible Embed
 * Plugin URI:  https://gist.github.com/westonruter/8199d0fcb417a909380b0aeff4247cf7
 * Description: Modify YouTube embeds to include additional IFrame Player API parameters to improve accessibility.
 * Version:     0.1.0
 * Author:      Weston Ruter
 * Author URI:  https://weston.ruter.net/
 * License:     GNU General Public License v2 (or later)
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 * Update URI:  false
 */

// Note: The embed_oembed_html filter can't be used because of Jetpack.
add_filter(
	'the_content',
	static function ( $content ) {
		if ( ! class_exists( 'WP_HTML_Tag_Processor' ) ) {
			return $content;
		}

		$p = new WP_HTML_Tag_Processor( $content );
		while ( $p->next_tag( [ 'tag_name' => 'iframe' ] ) ) {
			$src = $p->get_attribute( 'src' );
			if (
				is_string( $src )
				&&
				wp_parse_url( $src, PHP_URL_HOST ) === 'www.youtube.com'
				&&
				str_starts_with( wp_parse_url( $src, PHP_URL_PATH ), '/embed/' )
			) {
				$src = add_query_arg(
					[
						'rel'            => '0', // See <https://developers.google.com/youtube/player_parameters?csw=1#rel>.
						'fs'             => '0', // See <https://developers.google.com/youtube/player_parameters?csw=1#fs>.
						'modestbranding' => '1', // See <https://developers.google.com/youtube/player_parameters?csw=1#modestbranding>.
					],
					$src
				);
				$p->set_attribute( 'src', $src );
			}
		}
		return $p->get_updated_html();
	},
	100
);