Generate a WordPress plugin for Mailchimp signup sync
Pushing contacts to Mailchimp from WordPress is the classic integration. The first step (a signup form) is solved by the official Mailchimp plugin. Where that plugin stops is where custom business logic starts: syncing WooCommerce customers with their purchase history as merge fields, tagging contacts based on which category they bought from, moving users between audiences when their plan changes, respecting GDPR consent from your own UI rather than Mailchimp's hosted form.
A custom Mailchimp plugin is a thin wrapper around the v3 API with your exact mapping. We use the key-datacenter API key format (the shop owner pastes it in settings), respect Mailchimp rate limits, and queue writes so a slow Mailchimp response never degrades your front-end.
Why generate it instead of installing an existing plugin?
MC4WP (Mailchimp for WordPress) is excellent and free for basic signup forms. Its premium addons (€89+/year) unlock user integrations and custom merge fields. If your case involves custom triggers beyond the standard form, paying for the addon is reasonable — so is generating a plugin scoped to your exact triggers.
Once you add complex tagging logic ("tag this contact with category-X if they ordered a product from category X, within 30 days"), a generated plugin following your exact rules is cleaner than composing them in the admin UI of a generic plugin. Your rules live in code, reviewable, versionable, and the output is predictable.
Mailchimp rate limits (10 concurrent connections per API key) get tripped often with store-wide sync scripts. A generated plugin uses a proper queue and serial write pattern, which stays within limits on any account size.
Example prompt
This is the kind of description that generates this plugin. You can start from it and tweak whatever you need before hitting generate.
Plugin name: Acme MC Sync
Triggers:
1. Form submission (Gravity Forms form ID 2): add to list ID "abc123" with merge fields FNAME, LNAME, COMPANY. Tag: "contact_form".
2. WooCommerce order completed: add customer to list ID "def456". Merge fields: FNAME, LNAME, LASTPURCH (date), TOTALSPENT. Tags based on purchased categories ("bought_shoes", "bought_accessories", etc.).
3. User registration: add to list ID "ghi789" with tag "user".
Double opt-in: off (we have own consent in the form / checkout).
On sync error: retry twice with a 5-second delay; if still failing, log to wp_options and email admin once per hour.
Admin page:
- API key (key-datacenter format) in a password field.
- List IDs per trigger.
- Tag mapping table (WC category → Mailchimp tag).
- Suppression list (emails that should never be synced).
HPOS-compatible. No DB tables (uses options for suppression list).What the generated plugin typically includes
- Mailchimp API v3 client using wp_remote_post (no Composer needed)
- Service class encapsulating subscribe/update/tag operations with idempotency (uses MD5 of lowercase email)
- Hook wiring for form, order and user events
- Queued async writes via WP Cron to stay within rate limits
- Mapping UI in the admin for category → tag rules
- Suppression list stored in an option with autoload=no
- HPOS-compatible order reads
Swap Mailchimp for Brevo, ActiveCampaign, MailerLite, Klaviyo. Adapter pattern changes auth + endpoint; the rest stays.
Frequently asked questions
Does this replace MC4WP?
If MC4WP free covers your use case, keep it. If you need the premium features anyway, a generated plugin is often the same effort and gives you more control. They can coexist if you only use this one for specific custom triggers.
What about GDPR consent?
The plugin only syncs contacts who have given consent through your form / checkout UI. Consent status is stored locally and passed to Mailchimp as a compliance note. If a user requests erasure, the plugin removes them from Mailchimp via the members archive API.
How does it handle double opt-in?
Configurable per list. By default off because you typically already have consent from your own form; you can enable it per list if your compliance officer prefers it.
What if my Mailchimp account has 100k contacts?
Incremental sync (only new/updated contacts) avoids any full catalogue pass. For the initial seed, we include a WP-CLI command that paginates through users/orders in the background.