start.php

<?php
/**
 * Elgg welcome plugin start
 *
 * @author Gerard Kanters
 * @author Wouter van Os
 * @author Juho Jaakkola
 *
 * @website https://www.centillien.com
 *
 * @copyright Centillien 2016
 */

elgg_register_event_handler('init', 'system', 'welcome_init');

/**
 * Initialize the plugin
 */
function welcome_init()
{
    if (elgg_is_admin_logged_in()) {
       elgg_unregister_plugin_hook_handler('validate', 'input', 'htmlawed_filter_tags');
    }
    elgg_register_page_handler('welcome', 'welcome_page_handler');

    elgg_register_plugin_hook_handler('forward', 'system', 'welcome_forward_hook', 600);

    //Register action path for email change
    $action_path = dirname(__FILE__) . '/actions';
    elgg_register_action('welcome/change_user_email', "$action_path/change_user_email.php", 'public');
    elgg_register_ajax_view('welcome/change_email');

    //Support for walled garden
    elgg_register_plugin_hook_handler('public_pages', 'walled_garden', 'welcome_public_pages');
}

/**
 * Directs user to welcome page after successful registration
 *
 * @param string $hook_name 'forward'
 * @param string $type 'system'
 * @param string $return The url that user is being forwarded to
 * @param array $params Hook parameters
 *
 * @return string $forward_url The new forward url
 */
function welcome_forward_hook($hook_name, $type, $return, $params)
{
    $current = current_page_url();

    // Check whether user is being forwarded from the registration action
    if (strpos($current, 'action/register') === false) {
        return $return;
    }

    $username = get_input('username');

    // User validation by email has disabled the user so we need to
    // explicitly include hidden entities in the database query
    $hidden_status = access_get_show_hidden_status();
    access_show_hidden_entities(true);

    $user = get_user_by_username($username);

    // Set hidden entity status back to normal
    access_show_hidden_entities($hidden_status);

    if (!$user) {
        // User does not exist meaning that registration failed
        return $return;
    }

    // Pass on the user GUID in the url so the welcome page can access the user
    $welcome_url = elgg_normalize_url('welcome/' . $user->guid);

    return $welcome_url;
}

/**
 * Handle requests to /welcome/
 *
 * @param array $page Page segments
 *
 * @return boolean
 */
function welcome_page_handler($page)
{
    // User validation by email has disabled the user so we need to
    // explicitly include hidden entities in the database query
    $hidden_status = access_get_show_hidden_status();
    access_show_hidden_entities(true);

    $user = get_user($page[0]);

    // Set hidden entity status back to normal
    access_show_hidden_entities($hidden_status);

    if (!$user) {
        forward();
    }

    set_input('guid', $user->guid);

    $base = elgg_get_plugins_path() . 'welcome/pages/';

    switch ($page[0]) {
        default:
            include $base . '/welcome.php';
            break;
    }

    return true;
}

/**
 * Extend public pages for walled garden
 *
 * @param string $hook_name 'public_pages'
 * @param string $entity 'walled_garden'
 * @param array $return_value Array of public pages
 * @param array $params Hook parameters
 *
 * @return array
 */
function welcome_public_pages($hook_name, $entity, $return, $params)
{
    $return[] = "welcome/*"; // for backwards compatibility
    $return[] = 'welcome\/[0-9]+';

    return $return;
}

/**
 * Validate a e-mail adress on it's domain, check
 * if an MX records exists for that domain.
 *
 * @param string $email E-mail address to validate
 *
 * @return bool
 */
function checkEmail($email)
{
    // Get domain from e-mailadres
    list(,$domain) = explode('@', $email);

    // Check if MX record exists for domain
    if (!checkdnsrr($domain, 'MX')) {
        return false;
    } else {
        return true;
    }
}