Build an add-on

1 · Anatomy of an add-on

Plugin header

Declare a dependency on the core plugin so WordPress itself warns when it's missing, and mark it network-capable:

<?php
/**
 * Plugin Name:       Kjeks Google
 * Description:       Google Tag Manager / GA4 for Kjeks via Consent Mode v2.
 * Requires at least: 6.8
 * Requires PHP:      8.3
 * Requires Plugins:  kjeks          // WordPress warns if Kjeks is missing
 * Network:           true           // multisite-friendly, like the core plugin
 */

Boot only when Kjeks is present

The Requires Plugins: kjeks header already stops WordPress from activating your add-on without Kjeks (and from deactivating Kjeks while yours is active). So you don't need a dependency class — a one-linefunction_exists() guard on the core plugin's public API is enough insurance for the rare “active but not loaded” edge:

add_action(
    'plugins_loaded',
    static function (): void {
        // The Requires Plugins header prevents activation without Kjeks; this
        // one-liner is cheap insurance for the "active but API not loaded" edge.
        if ( ! function_exists( 'kjeks_register_integration' ) ) {
            return;
        }
        Plugin::instance()->boot();
    }
);

2 · Register your technology

This is the heart of every add-on. Hook thekjeks_register_integrations action and callkjeks_register_integration( $id, $args ). Kjeks blocks the scripts until the category is granted:

add_action( 'kjeks_register_integrations', function (): void {
    kjeks_register_integration(
        'google-tags',                    // unique integration id
        array(
            'category'    => 'analytics', // gate: runs only when this is granted
            'label'       => 'Google Tag Manager / Analytics',
            'src_scripts' => array(
                'https://www.googletagmanager.com/gtag/js?id=G-XXXXXXX',
            ),
            'inline'      => array(
                "gtag('js', new Date()); gtag('config', 'G-XXXXXXX');",
            ),
            // 'handles' => array( 'my-registered-handle' ), // or gate an already-enqueued script
        )
    );
} );

The arguments

3 · React to consent on the front end

Registration is enough for most add-ons — Kjeks loads your scripts when consent is granted. But some technologies (like Google Consent Mode) must alsosignal on every change. Kjeks gives you a small JS surface:window.kjeks.isGranted( category ) and thekjeks:granted / kjeks:withdrawn events.

// Consent Mode v2 defaults — printed in wp_head BEFORE anything Google loads.
gtag( 'consent', 'default', {
    ad_storage: 'denied', ad_user_data: 'denied',
    ad_personalization: 'denied', analytics_storage: 'denied',
    wait_for_update: 500,
} );

// Sync to Kjeks now and on every change.
function granted( c ) {
    return window.kjeks ? window.kjeks.isGranted( c ) : false;
}
function apply() {
    if ( typeof gtag !== 'function' ) return;
    gtag( 'consent', 'update', {
        analytics_storage: granted( 'analytics' ) ? 'granted' : 'denied',
        ad_storage:        granted( 'marketing' ) ? 'granted' : 'denied',
    } );
}
window.addEventListener( 'kjeks:granted', apply );
window.addEventListener( 'kjeks:withdrawn', apply );
document.addEventListener( 'DOMContentLoaded', apply );

kjeks-google prints the first block (defaults denied) in wp_head at priority 1, and the sync block at priority 2 — so Google's own state isdenied until Kjeks says otherwise, a second layer on top of the gate.

4 · Settings, config & updates

Store configuration

kjeks-google keeps a network default (kjeks_google_network) and a per-site override (kjeks_google), resolved so a site's own value wins. Expose a settings page on network_admin_menu (capabilitymanage_network_options) and admin_menu (capabilitymanage_options), mirroring how the core plugin adapts to single-site vs multisite.

Offer a filter

Let other code adjust your resolved config at runtime:

add_filter( 'kjeks_google_config', function ( $config, $blog_id ) {
    // $config = [ 'gtm_id' => '', 'ga4_id' => 'G-XXXX', 'gating_category' => 'analytics' ]
    return $config;
}, 10, 2 );

Ship self-updates (optional)

Add soderlind/wordpress-github-updater via Composer and callGitHubUpdater::init() in your main file, exactly like the rest of the family — see any add-on's bootstrap for the pattern.

Study the full example in the kjeks-google repository, and see the core developer guide for the complete integration API.