Remove a WP user capability from a user **after** the user registers for an Event Espresso event.

remove_one_time_invitation_from_user.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

add_action('AHEE__EE_Registration_Processor__trigger_registration_update_notifications', 'my_remove_one_time_invitation_from_user');
function my_remove_one_time_invitation_from_user() {
  if (current_user_can( 'has_unique_invitation_code' )){
    $user = new WP_User( get_current_user_id() );
    $user->remove_cap( 'has_unique_invitation_code' );
  }
}

usage.md

Usage Notes

1. Use a script, see below, or a plugin like the User Role Editor plugin to create a new capability and grant that capability to user accounts. In this example the capability is has_unique_invitation_code.
2. Use the WP User Integration add-on’s feature to set the ticket requirement capability:
3. Add the above code to automatically remove that capability after they register for the event: You can add the above to a functions plugin.

wp_add_user_caps_on_activate.php

<?php
/*
Plugin Name: Add User Capability on Activation
Description: Adds a capability to an array of user accounts specified by email address. Deactivate and delete this plugin after activation.
Version: 1.0
*/

function add_user_caps_on_activate() {
  $selectedUserEmails = 
    array(
      'example1@example.com',
      'example2@example.com',
      'example3@example.com',
      // and more added here
    );
  foreach ( $selectedUserEmails as $userEmail ) { 
    if ( filter_var( $userEmail, FILTER_VALIDATE_EMAIL ) ) {
      $user = get_user_by( 'email', $userEmail );
      if ( ! empty( $user ) ) {
        $user->add_cap( 'has_unique_invitation_code' );
      }
    }
  }
}
register_activation_hook( __FILE__, 'add_user_caps_on_activate' );