Prototypux SaaS Engine is a lightweight bridge between billing and permissions. It translates the state of a Stripe subscription into WordPress entitlements — a managed role, publishing quotas, and plan-based access — so you can monetize any WordPress site without gluing together form plugins, Stripe feeds and fragile role-switching code.

It is not a traditional membership plugin. Stripe does what Stripe does best (hosted Checkout, dunning, the Customer Portal, receipts, promotion codes, tax); the plugin owns your plans, subscription state, roles and quotas.

What it does

Plans as a custom post type: type (free/paid), monthly and/or yearly price, managed role, publishing quotas, fallback plan, and a manual features list for the pricing table.
Quotas on as many content types as you need — pick them once in Settings, then give every plan its own limit for each (posts, listings, a custom post type, or all of them).
Freemium without trials: a permanent free plan is assigned automatically on registration (by any form or builder). Upgrades go through Stripe.
Hosted Stripe Checkout & Customer Portal — cards never touch your site (PCI SAQ-A). No embedded SDK: a thin HTTP client with a pinned API version and signed webhooks.
Activation by webhook only — access is never granted on the checkout redirect, so a closed browser tab never leaves a customer half-subscribed.
Server-side quota enforcement — publishing limits are enforced in the REST API and on post insert, not just hidden in the UI. Quota = items published (or scheduled) at once; deleting one frees a slot.
A static checkout URL you can paste into any button, menu or email, plus a Customer Portal link.
Account components as shortcodes: pricing table, plan status, usage bars, portal & checkout buttons, plan/quota conditionals, and CSS visibility classes for page builders.
Manual reconciliation with Stripe (Tools) — the one-click repair for a missed webhook.
Automatic past-due banner for the affected user, linking to the Customer Portal.

Shortcodes

[wpse_pricing] — pricing table with a monthly/yearly toggle and manual feature lists.
[wpse_account] — a pre-assembled account page.
[wpse_plan_status], [wpse_usage type="post"], [wpse_portal_button], [wpse_checkout_button plan="basic" interval="month"]
[wpse_if_plan plan="pro,basic"]…[/wpse_if_plan] (add not="1" to invert)
[wpse_can_create type="post"]…[/wpse_can_create] and its opposite [wpse_quota_reached type="post"]…[/wpse_quota_reached]
[wpse_quota_remaining type="post"] and [wpse_quota_message type="post"]

Body CSS classes for builders

For every content type a plan limits, the plugin exposes ready-made classes you can drop onto any element in your page builder:

wpse-hide-if-quota-full-{type} — hides the element once the quota is full.
wpse-show-if-quota-full-{type} — shows the element only when the quota is full.

Plus wpse-plan-{slug}, wpse-status-{status}, wpse-can-create-{type} / wpse-quota-full-{type} on the body for custom CSS.

Developer API

Public functions (wpse_subscription(), wpse_has_plan(), wpse_quota(), wpse_can_create(), wpse_checkout_url()), actions (wpse_activated, wpse_status_changed, wpse_payment_completed, wpse_downgraded, wpse_quota_reached, wpse_quota_demoted) and filters let you extend everything from your own theme or plugin.

External services

This plugin connects to the Stripe API (https://api.stripe.com) to create and manage subscriptions. Stripe is the payment processor; without it the plugin cannot sell or manage paid plans. No other external service is contacted, and the plugin loads no scripts, styles or fonts from third-party servers.

Data is sent to Stripe only in these situations:

When an administrator syncs a plan (Plans Sync with Stripe): the plan name, price amounts, currency and billing interval. No personal data.
When a logged-in user starts a checkout: their email address, display name, WordPress user ID, the plan ID and your site URL, so Stripe can create the customer record and the plugin can match the resulting subscription back to the right user.
When a logged-in user opens the Customer Portal: their Stripe customer ID.
When an administrator runs Tools Reconcile: the plugin requests subscription and invoice data from Stripe for the subscriptions stored on your site.

Stripe also sends data to your site through the webhook endpoint (/wp-json/wpse/v1/webhook): subscription and invoice events, whose signature is verified before being processed. Received events are stored in a database table for auditing and are deleted automatically after a configurable retention period (90 days by default).

The service is provided by Stripe, Inc.:

You need your own Stripe account and API keys, and you are responsible for informing your users, in your own privacy policy, that payment data is processed by Stripe.