Generate invite codes for all users with a certain membership level.

my_init.php

<?php

/*
 * Generate invite codes for all users with a certain membership level.
 */
function my_init() {
	if ( ! empty( $_REQUEST['create_invites'] ) && current_user_can( 'manage_options' ) ) {

		global $wpdb;

		// change level here
		$level_id = 1;

		// get all users with specific membership level
		$sql = "SELECT user_id FROM $wpdb->pmpro_memberships_users WHERE membership_id=" . $level_id . " AND status='active'";
		$users = $wpdb->get_col($sql);
		
		// create codes for them
		foreach($users as $user_id)
			pmproio_createInviteCodes($user_id);
	}
}

add_filter( 'init', 'my_init' );