Documentation

Developer reference

Availo is built to be extended. This is the same hook layer that Availo Pro itself uses — nothing is private API.

Actions
Filters
The slot engine
REST API
Webhook payload
Capabilities
Data storage

Actions

Fired on the booking lifecycle. Handlers receive the booking as an associative array (the database row) and the EventType object.

// A booking was created (confirmed, or pending under approval mode).
do_action( 'availo_booking_created', array $booking, EventType $event, string $raw_token );

// A pending booking was approved (Pro). Sends the confirmation email + .ics.
do_action( 'availo_booking_approved', array $booking, ?EventType $event );

// A booking was cancelled (by invitee, admin, or a declined request).
do_action( 'availo_booking_cancelled', array $booking, ?EventType $event );

// A booking was rescheduled — a new booking is created, the old one marked.
do_action( 'availo_booking_rescheduled', array $new_booking, array $old_booking, EventType $event, string $raw_token );

// A reminder is due for a confirmed, upcoming booking.
do_action( 'availo_booking_reminder', array $booking, ?EventType $event );

$raw_token is the unhashed manage token, available only at creation time — use it to build a manage URL with \Availo\Frontend\BookingPageRouter::manage_url( $raw_token ).

Example — post to Slack on every booking:

add_action( 'availo_booking_created', function ( $booking, $event ) {
    if ( 'confirmed' !== $booking['status'] ) {
        return;
    }
    wp_remote_post( 'https://hooks.slack.com/services/XXX', array(
        'body' => wp_json_encode( array(
            'text' => sprintf( 'New booking: %s with %s', $event->title, $booking['invitee_name'] ),
        ) ),
    ) );
}, 10, 2 );

Filters

// Modify a booking row before it is inserted (runs inside the per-host lock,
// after availability validation). Pro uses this for approval status, host
// assignment, and attaching Zoom/Meet links.
apply_filters( 'availo_booking_data', array $data, EventType $event, DateTimeImmutable $start );

// Adjust the slot-engine configuration before slots are computed. Add busy
// intervals here to block time from external sources.
apply_filters( 'availo_slot_config', array $config, EventType $event );

// Filter the computed availability. Receives the range so you can compute
// additional hosts' availability for the same window.
apply_filters( 'availo_available_slots', array $slots, EventType $event,
    DateTimeImmutable $range_start, DateTimeImmutable $range_end,
    DateTimeZone $invitee_tz, DateTimeImmutable $now );

// Add row actions (e.g. Approve/Decline) to bookings in the admin list.
apply_filters( 'availo_booking_row_actions', array $actions, array $item );

// Return false to suppress the confirmation/notification emails for a booking
// (reminders and integrations still run).
apply_filters( 'availo_send_booking_emails', bool $send, array $booking, EventType $event );

// Customize email bodies before merge tags are applied.
apply_filters( 'availo_email_confirmation_body', string $body, array $booking, EventType $event );
apply_filters( 'availo_email_pending_body',      string $body, array $booking, EventType $event );
apply_filters( 'availo_email_reminder_body',     string $body, array $booking, ?EventType $event );

Example — block time from an external source:

add_filter( 'availo_slot_config', function ( $config, $event ) {
    $config['busy'][] = array(
        'start'         => new DateTimeImmutable( '2026-08-01 09:00:00', new DateTimeZone( 'UTC' ) ),
        'end'           => new DateTimeImmutable( '2026-08-01 12:00:00', new DateTimeZone( 'UTC' ) ),
        'event_type_id' => 0, // 0 = external; never counts toward the daily cap.
    );
    return $config;
}, 10, 2 );

The slot engine

The core availability calculation lives in \Availo\Core\SlotEngine. It’s pure PHP with no WordPress dependencies — given a configuration array, a date range, and a time zone, it returns available start times grouped by day. All arithmetic is in UTC using IANA time zones, so daylight-saving transitions are handled correctly.

\Availo\Core\Availability::slots_for_range() is the WordPress-aware wrapper that assembles the config from an event type, its schedule, and existing bookings, then applies the filters above.

REST API

The booking widget talks to a public REST namespace, availo/v1:

Route	Method	Purpose
`/slots`	GET	Available slots for an event type and month
`/bookings`	POST	Create a booking
`/bookings/{token}`	GET	Fetch a booking by its manage token
`/bookings/{token}/cancel`	POST	Cancel a booking
`/bookings/{token}/reschedule`	POST	Reschedule a booking
`/bookings/{token}/ics`	GET	Download the .ics for a booking

These power the front-end widget. The manage routes are authenticated by the 256-bit token in the URL; creation is rate-limited and protected against spam.

Webhook payload

(Pro.) Each webhook delivery is an HTTP POST with a JSON body:

{
  "event": "booking.created",
  "created_at": "2026-07-13T09:00:00+00:00",
  "data": {
    "booking_id": 123,
    "status": "confirmed",
    "start_utc": "2026-07-20 14:00:00",
    "end_utc": "2026-07-20 14:30:00",
    "invitee_name": "Jane Cooper",
    "invitee_email": "jane@example.com",
    "invitee_timezone": "America/New_York",
    "location": "https://zoom.us/j/…",
    "source": "web",
    "event_type": { "id": 5, "title": "Discovery Call", "slug": "discovery-call" },
    "manage_url": "https://yoursite.com/schedule/manage/…/"
  }
}

When a secret is configured, verify the X-Availo-Signature header — sha256=<HMAC-SHA256 of the raw request body, keyed with your secret>.

Capabilities

Capability	Granted to	Controls
`availo_view_bookings`	Admin, Host	Access to the bookings, calendar, add-booking screens
`availo_manage_availability`	Admin, Host	Editing availability
`availo_manage_others_bookings`	Admin only	Seeing/managing every host’s bookings
`edit_availo_events` (+ related)	Admin, Host	Managing event types

The Availo Host role (availo_host) bundles the host capabilities.

Data storage

Event types are a custom post type (availo_event); their settings are post meta.
Bookings, booking meta, schedules, schedule rules, and schedule overrides are custom database tables (prefixed availo_), designed for fast date-range queries and safe concurrent booking.

Manage tokens are stored hashed; personal data lives only in the booking tables, giving a single place for the GDPR tools to operate.