An abstractor for links in ACF WYSIWYG fields.

ACFLinkAbstractor.php

<?php

/*
 * Copyright (c) Rasso Hilber
 * https://rassohilber.com
 * License: MIT
 */

namespace Site\Base;

/**
 * An abstractor for links in ACF WYSIWYG fields.
 * Parses arbitrary URLs in your links and attempts to save them as post IDs.
 *
 * Helps preventing dead links when linked posts get deleted or changed.
 *
 * Call like this: ACFLinkAbstractor::init();
 */
class ACFLinkAbstractor
{
    public static function init(): void
    {
        add_filter('acf/update_value/type=wysiwyg', [self::class, 'abstractLinks'], 1, 3);
        add_filter('acf/load_value/type=wysiwyg', [self::class, 'deAbstractLinks'], 1, 3);
    }

    /**
     * Abstract links (from permalink to {{link:ID}})
     */
    public static function abstractLinks(mixed $value, int|string $post_id, array $field): mixed
    {
        if (!is_string($value) || trim($value) === '') {
            return $value;
        }

        $value = wp_unslash($value);

        $replaced = preg_replace_callback(
            '#<a\s+[^>]*href=["\']([^"\']+)["\'][^>]*>(.*?)</a>#i',
            function ($matches) {
                $href = $matches[1];
                $text = $matches[2];

                $linkID = self::getLinkID($href);

                if ($linkID) {
                    return sprintf('<a href="{{link:%s}}">%s</a>', $linkID, $text);
                }

                return $matches[0];
            },
            $value
        );

        return $replaced;
    }

    /**
     * De-abstracts links (from {{link:ID}} to permalinks)
     */
    public static function deAbstractLinks(mixed $value, int|string $post_id, array $field): mixed
    {
        if (!is_string($value) || trim($value) === '') {
            return $value;
        }

        return preg_replace_callback(
            '#<a\s+[^>]*href=["\']\{\{link:(\d+)\}\}["\'][^>]*>(.*?)</a>#i',
            function ($matches) {
                $raw = $matches[0];
                $postID = (int) $matches[1];
                $url = get_permalink($postID);
                $text = $matches[2];

                if (!$url || get_post_status($postID) !== 'publish') {
                    return function_exists('get_current_screen') ? $raw : $text;
                }

                return sprintf('<a href="%s">%s</a>', esc_url($url), $text);
            },
            $value
        );
    }

    /**
     * Attempt to get an ID from a URL. Currently only implemented for posts.
     */
    private static function getLinkID(string $url): ?string
    {
        $query = self::resolveURL($url);

        if (!$queriedObject = $query->get_queried_object()) {
            return null;
        }

        return match($queriedObject::class) {
            'WP_Post' => "$queriedObject->ID",
            default => null
        };
    }

    /**
     * Attempt to resolve a URL to a WP_Query.
     * Works for custom post types, too.
     * Like url_to_postid() on stereoids.
     * Could even be extended to support custom post type archives
     * or WP_Term links
     * @see https://developer.wordpress.org/reference/functions/url_to_postid/
     */
    private static function resolveURL(?string $url = null): \WP_Query
    {
        /**
         * @global \WP $wp
         * @global \WP_Query $wp_the_query
         */
        global $wp, $wp_the_query;

        $url ??= home_url($_SERVER['REQUEST_URI']);
        $path = self::getPathRelativeToHomeURL($url);

        remove_action('parse_request', 'rest_api_loaded');

        /** Augment $_SERVER as WP relies on it to parse query vars */
        $__SERVER = $_SERVER;
        /** Write the path in REQUEST_URI */
        $_SERVER['REQUEST_URI'] = $path;
        /** Trick WP into thinking it's on the frontend: */
        $_SERVER['PHP_SELF'] = 'index.php';

        /**
         * Construct a new WP instance based on our augmented $_SERVER.
         * We'll need the query_vars from this new instance later in our custom WP_Query.
         */
        $newWP = new \WP();
        $newWP->public_query_vars = $wp->public_query_vars;
        $newWP->parse_request();
        $newWP->build_query_string();
        $queryVars = $newWP->query_vars;

        /** Revert the augmented $_SERVER */
        $_SERVER = $__SERVER;

        /** Store the global WP_Query so that we can revert it later  */
        $_wp_the_query = $wp_the_query;
        $query = new \WP_Query();
        /**
         * Makes `$query->is_main_query()` return true for this query.
         * That way, all relevant filters will be applied as expected.
         */
        $wp_the_query = $query;
        /** Inject the query_vars from our new WP instance created above */
        $query->query($queryVars);
        /** Revert the augmented global WP_Query */
        $wp_the_query = $_wp_the_query;

        add_action('parse_request', 'rest_api_loaded');

        return $query;
    }

    /**
     * Get the path relative to home
     */
    private static function getPathRelativeToHomeURL(string $url): string
    {
        $homeURL = home_url();
        $homePath = parse_url($homeURL, PHP_URL_PATH) ?: '';
        $fullPath = wp_parse_url($url, PHP_URL_PATH) ?: '';

        return '/' . ltrim(substr($fullPath, strlen($homePath)), '/');
    }
}