civicrm.php

<?php
/**
 * Plugin Name: CiviCRM
 * Description: CiviCRM - Growing and Sustaining Relationships
 * Version: 5.39.1
 * Requires at least: 4.9
 * Requires PHP:      7.2
 * Author: CiviCRM LLC
 * Author URI: https://civicrm.org/
 * Plugin URI: https://docs.civicrm.org/sysadmin/en/latest/install/wordpress/
 * License: AGPL3
 * Text Domain: civicrm
 * Domain Path: /languages
 */

/*
 +--------------------------------------------------------------------+
 | Copyright CiviCRM LLC. All rights reserved.                        |
 |                                                                    |
 | This work is published under the GNU AGPLv3 license with some      |
 | permitted exceptions and without any warranty. For full license    |
 | and copyright information, see https://civicrm.org/licensing       |
 +--------------------------------------------------------------------+
 */

/**
 *
 * @package CRM
 * @copyright CiviCRM LLC https://civicrm.org/licensing
 *
 */

/*
 * -----------------------------------------------------------------------------
 * WordPress resources for developers
 * -----------------------------------------------------------------------------
 * Not that they're ever adhered to anywhere other than core, but people do their
 * best to comply...
 *
 * WordPress core coding standards:
 * https://developer.wordpress.org/coding-standards/wordpress-coding-standards/php/
 *
 * WordPress HTML standards:
 * https://make.wordpress.org/core/handbook/best-practices/coding-standards/html/
 *
 * WordPress JavaScript standards:
 * https://developer.wordpress.org/coding-standards/wordpress-coding-standards/javascript/
 * -----------------------------------------------------------------------------
 */

// This file must not accessed directly.
if (!defined('ABSPATH')) {
  exit;
}

// Set version here: when it changes, will force Javascript & CSS to reload.
define('CIVICRM_PLUGIN_VERSION', '5.39.1');

// Store reference to this file.
if (!defined('CIVICRM_PLUGIN_FILE')) {
  define('CIVICRM_PLUGIN_FILE', __FILE__);
}

// Store URL to this plugin's directory.
if (!defined('CIVICRM_PLUGIN_URL')) {
  define('CIVICRM_PLUGIN_URL', plugin_dir_url(CIVICRM_PLUGIN_FILE));
}

// Store PATH to this plugin's directory.
if (!defined('CIVICRM_PLUGIN_DIR')) {
  define('CIVICRM_PLUGIN_DIR', plugin_dir_path(CIVICRM_PLUGIN_FILE));
}

if (!defined('CIVICRM_WP_PHP_MINIMUM')) {
  /**
   * Minimum required PHP.
   *
   * Note: This duplicates `CRM_Upgrade_Incremental_General::MIN_INSTALL_PHP_VER`.
   * The duplication helps avoid dependency issues. (Reading
   * `CRM_Upgrade_Incremental_General::MIN_INSTALL_PHP_VER` requires loading
   * `civicrm.settings.php`, but that triggers a parse-error on PHP 5.x.)
   *
   * @see CRM_Upgrade_Incremental_General::MIN_INSTALL_PHP_VER
   * @see CiviWP\PhpVersionTest::testConstantMatch()
   */
  define('CIVICRM_WP_PHP_MINIMUM', '7.2.0');
}

/*
 * The constant `CIVICRM_SETTINGS_PATH` is also defined in `civicrm.config.php`
 * and may already have been defined there - e.g. by cron or external scripts.
 */
if (!defined('CIVICRM_SETTINGS_PATH')) {

  /*
   * Test where the settings file exists.
   *
   * If the settings file is found in the 4.6 and prior location, use that as
   * `CIVICRM_SETTINGS_PATH`, otherwise use the new location.
   */
  $upload_dir = wp_upload_dir();
  $wp_civi_settings = $upload_dir['basedir'] . DIRECTORY_SEPARATOR . 'civicrm' . DIRECTORY_SEPARATOR . 'civicrm.settings.php';
  $wp_civi_settings_deprectated = CIVICRM_PLUGIN_DIR . 'civicrm.settings.php';

  if (file_exists($wp_civi_settings_deprectated)) {
    define('CIVICRM_SETTINGS_PATH', $wp_civi_settings_deprectated);
  }
  else {
    define('CIVICRM_SETTINGS_PATH', $wp_civi_settings);
  }

}

// Test if CiviCRM is installed.
if (file_exists(CIVICRM_SETTINGS_PATH)) {
  define('CIVICRM_INSTALLED', TRUE);
}
else {
  define('CIVICRM_INSTALLED', FALSE);
}

// Prevent CiviCRM from rendering its own header.
define('CIVICRM_UF_HEAD', TRUE);

/**
 * Setting this to 'TRUE' will replace all mailing URLs calls to 'extern/url.php'
 * and 'extern/open.php' with their REST counterpart 'civicrm/v3/url' and
 * 'civicrm/v3/open'.
 *
 * Use for test purposes, may affect mailing performance.
 *
 * @see CiviCRM_WP_REST\Plugin::replace_tracking_urls()
 */
if (!defined('CIVICRM_WP_REST_REPLACE_MAILING_TRACKING')) {
  define('CIVICRM_WP_REST_REPLACE_MAILING_TRACKING', FALSE);
}

/**
 * Define CiviCRM_For_WordPress Class.
 *
 * @since 4.4
 */
class CiviCRM_For_WordPress {

  /**
   * @var object
   * Plugin instance.
   * @since 4.4
   * @access private
   */
  private static $instance;

  /**
   * @var bool
   * Plugin context (broad).
   * @since 4.4
   * @access public
   */
  public static $in_wordpress;

  /**
   * @var string
   * Plugin context (specific).
   * @since 4.4
   * @access public
   */
  public static $context;

  /**
   * @var object
   * Shortcodes management object.
   * @since 4.4
   * @access public
   */
  public $shortcodes;

  /**
   * @var object
   * Modal dialog management object.
   * @since 4.4
   * @access public
   */
  public $modal;

  /**
   * @var object
   * Basepage management object.
   * @since 4.4
   * @access public
   */
  public $basepage;

  /**
   * @var object
   * User management object.
   * @since 4.4
   * @access public
   */
  public $users;

  /**
   * @var object
   * The plugin compatibility object.
   * @since 5.24
   * @access public
   */
  public $compat;

  /**
   * @var object
   * Admin object.
   * @since 5.33
   * @access public
   */
  public $admin;

  // ---------------------------------------------------------------------------
  // Setup
  // ---------------------------------------------------------------------------

  /**
   * Getter method which returns the CiviCRM instance and optionally creates one
   * if it does not already exist. Standard CiviCRM singleton pattern.
   *
   * @since 4.4
   *
   * @return object CiviCRM_For_WordPress The CiviCRM plugin instance.
   */
  public static function singleton() {

    // If instance doesn't already exist.
    if (!isset(self::$instance)) {

      // Create instance.
      self::$instance = new CiviCRM_For_WordPress();

      // Delay setup until 'plugins_loaded' to allow other plugins to load as well.
      add_action('plugins_loaded', [self::$instance, 'setup_instance']);

    }

    // Return instance.
    return self::$instance;

  }

  /**
   * Dummy instance constructor.
   *
   * @since 4.4
   */
  public function __construct() {}

  /**
   * Dummy magic method to prevent CiviCRM_For_WordPress from being cloned.
   *
   * @since 4.4
   */
  public function __clone() {
    _doing_it_wrong(__FUNCTION__, __('Only one instance of CiviCRM_For_WordPress please', 'civicrm'), '4.4');
  }

  /**
   * Dummy magic method to prevent CiviCRM_For_WordPress from being unserialized.
   *
   * @since 4.4
   */
  public function __wakeup() {
    _doing_it_wrong(__FUNCTION__, __('Please do not serialize CiviCRM_For_WordPress', 'civicrm'), '4.4');
  }

  /**
   * Plugin activation.
   *
   * This method is called only when CiviCRM plugin is activated. In order for
   * other plugins to be able to interact with CiviCRM's activation, we wait until
   * after the activation redirect to perform activation actions.
   *
   * @since 4.4
   */
  public function activate() {

    // Set a one-time-only option.
    add_option('civicrm_activation_in_progress', 'true');

  }

  /**
   * Run CiviCRM's plugin activation procedure.
   *
   * @since 4.4
   */
  public function activation() {

    // Bail if not activating.
    if (get_option('civicrm_activation_in_progress') !== 'true') {
      return;
    }

    // Bail if not in WordPress admin.
    if (!is_admin()) {
      return;
    }

    /**
     * Broadcast that activation actions need to happen now.
     *
     * @since 5.6
     */
    do_action('civicrm_activation');

    // Change option so this action never fires again.
    update_option('civicrm_activation_in_progress', 'false');
    if (!is_multisite() && !isset($_GET['activate-multi']) && !CIVICRM_INSTALLED) {
      wp_redirect(admin_url('options-general.php?page=civicrm-install'));
      exit;
    }
  }

  /**
   * Plugin deactivation.
   *
   * This method is called only when CiviCRM plugin is deactivated. In order for
   * other plugins to be able to interact with CiviCRM's activation, we need to
   * remove any options that are set in activate() above.
   *
   * @since 4.4
   */
  public function deactivate() {

    // Delete any options we hay have set.
    delete_option('civicrm_activation_in_progress');

    /**
     * Broadcast that deactivation actions need to happen now.
     *
     * @since 5.6
     */
    do_action('civicrm_deactivation');

  }

  // ---------------------------------------------------------------------------
  // Plugin set up
  // ---------------------------------------------------------------------------

  /**
   * Set up the CiviCRM plugin instance.
   *
   * @since 4.4
   */
  public function setup_instance() {

    // Kick out if another instance is being inited.
    if (isset(self::$in_wordpress)) {
      wp_die(__('Only one instance of CiviCRM_For_WordPress please', 'civicrm'));
    }

    // Maybe start session.
    $this->maybe_start_session();

    /*
     * AJAX calls do not set the 'cms.root' item, so make sure it is set here so
     * the CiviCRM doesn't fall back on flaky directory traversal code.
     */
    global $civicrm_paths;
    if (empty($civicrm_paths['cms.root']['path'])) {
      $civicrm_paths['cms.root']['path'] = untrailingslashit(ABSPATH);
    }
    if (empty($civicrm_paths['cms.root']['url'])) {
      $civicrm_paths['cms.root']['url'] = home_url();
    }

    // Include class files and instantiate.
    $this->include_files();
    $this->setup_objects();

    // Do plugin activation.
    $this->activation();

    // Use translation files.
    $this->enable_translation();

    // Register all hooks on init.
    add_action('init', [$this, 'register_hooks']);

    /**
     * Broadcast that this plugin is now loaded.
     *
     * @since 4.4
     */
    do_action('civicrm_instance_loaded');

  }

  /**
   * Maybe start a session for CiviCRM.
   *
   * There is no session handling in WordPress so start it for CiviCRM pages.
   *
   * Not needed when running:
   *
   * - via WP-CLI
   * - via wp-cron.php
   * - via PHP on the command line
   *
   * none of which require sessions.
   *
   * @since 5.28
   */
  public function maybe_start_session() {

    // Get existing session ID.
    $session_id = session_id();

    // Check WordPress pseudo-cron.
    $wp_cron = FALSE;
    if (function_exists('wp_doing_cron') && wp_doing_cron()) {
      $wp_cron = TRUE;
    }

    // Check WP-CLI.
    $wp_cli = FALSE;
    if (defined('WP_CLI') && WP_CLI) {
      $wp_cli = TRUE;
    }

    // Check PHP on the command line - e.g. `cv`.
    $php_cli = TRUE;
    if (PHP_SAPI !== 'cli') {
      $php_cli = FALSE;
    }

    // Maybe start session.
    if (empty($session_id) && !$wp_cron && !$wp_cli && !$php_cli) {
      session_start();
    }

  }

  /**
   * Include files.
   *
   * @since 4.4
   */
  public function include_files() {

    // Include class files.
    include_once CIVICRM_PLUGIN_DIR . 'includes/civicrm.admin.php';
    include_once CIVICRM_PLUGIN_DIR . 'includes/civicrm.users.php';
    include_once CIVICRM_PLUGIN_DIR . 'includes/civicrm.shortcodes.php';
    include_once CIVICRM_PLUGIN_DIR . 'includes/civicrm.shortcodes.modal.php';
    include_once CIVICRM_PLUGIN_DIR . 'includes/civicrm.basepage.php';
    include_once CIVICRM_PLUGIN_DIR . 'includes/civicrm.compat.php';

    // Maybe include REST API autoloader class.
    if (!class_exists('CiviCRM_WP_REST\Autoloader')) {
      require_once CIVICRM_PLUGIN_DIR . 'wp-rest/Autoloader.php';
    }

  }

  /**
   * Instantiate objects.
   *
   * @since 5.33
   */
  public function setup_objects() {

    // Instantiate objects.
    $this->admin = new CiviCRM_For_WordPress_Admin();
    $this->users = new CiviCRM_For_WordPress_Users();
    $this->shortcodes = new CiviCRM_For_WordPress_Shortcodes();
    $this->modal = new CiviCRM_For_WordPress_Shortcodes_Modal();
    $this->basepage = new CiviCRM_For_WordPress_Basepage();
    $this->compat = new CiviCRM_For_WordPress_Compat();

  }

  /**
   * Load translation files.
   *
   * A good reference on how to implement translation in WordPress:
   * http://ottopress.com/2012/internationalization-youre-probably-doing-it-wrong/
   *
   * Also see:
   * https://developer.wordpress.org/plugins/internationalization/
   *
   * @since 4.4
   */
  public function enable_translation() {

    // Load translations.
    load_plugin_textdomain(
      // Unique name.
      'civicrm',
      // Deprecated argument.
      FALSE,
      // Relative path to translation files.
      dirname(plugin_basename(__FILE__)) . '/languages/'
    );

  }

  // ---------------------------------------------------------------------------
  // Context
  // ---------------------------------------------------------------------------

  /**
   * Set broad CiviCRM context.
   *
   * Setter for determining if CiviCRM is currently being displayed in WordPress.
   * This becomes true whe CiviCRM is called in the following contexts:
   *
   * (a) in the WordPress back-end
   * (b) when CiviCRM content is being displayed on the front-end via wpBasePage
   * (c) when an AJAX request is made to CiviCRM
   *
   * It is NOT true when CiviCRM is called via a shortcode.
   *
   * @since 4.4
   */
  public function civicrm_in_wordpress_set() {

    // Get identifying query var.
    $page = get_query_var('civiwp');

    // Store.
    self::$in_wordpress = ($page == 'CiviCRM') ? TRUE : FALSE;

  }

  /**
   * Getter for testing if CiviCRM is currently being displayed in WordPress.
   *
   * @see $this->civicrm_in_wordpress_set()
   *
   * @since 4.4
   *
   * @return bool $in_wordpress True if CiviCRM is displayed in WordPress, false otherwise.
   */
  public function civicrm_in_wordpress() {

    /**
     * Allow broad context to be filtered.
     *
     * @since 4.4
     *
     * @param bool $in_wordpress True if CiviCRM is displayed in WordPress, false otherwise.
     * @return bool $in_wordpress True if CiviCRM is displayed in WordPress, false otherwise.
     */
    return apply_filters('civicrm_in_wordpress', self::$in_wordpress);

  }

  /**
   * Set specific CiviCRM context.
   *
   * Setter for determining how CiviCRM is currently being displayed in WordPress.
   * This can be one of the following contexts:
   *
   * (a) in the WordPress back-end
   * (b) when CiviCRM content is being displayed on the front-end via wpBasePage
   * (c) when a "non-page" request is made to CiviCRM
   * (d) when CiviCRM is called via a shortcode
   *
   * The following codes correspond to the different contexts:
   *
   * (a) 'admin'
   * (b) 'basepage'
   * (c) 'nonpage'
   * (d) 'shortcode'
   *
   * @since 4.4
   *
   * @param string $context One of the four context codes above.
   */
  public function civicrm_context_set($context) {

    // Store.
    self::$context = $context;

  }

  /**
   * Get specific CiviCRM context.
   *
   * Getter for determining how CiviCRM is currently being displayed in WordPress.
   *
   * @see $this->civicrm_context_set()
   *
   * @since 4.4
   *
   * @return string The context in which CiviCRM is displayed in WordPress.
   */
  public function civicrm_context_get() {

    /**
     * Allow specific context to be filtered.
     *
     * @since 4.4
     *
     * @param bool $context The existing context in which CiviCRM is displayed in WordPress.
     * @return bool $context The modified context in which CiviCRM is displayed in WordPress.
     */
    return apply_filters('civicrm_context', self::$context);

  }

  // ---------------------------------------------------------------------------
  // Hooks
  // ---------------------------------------------------------------------------

  /**
   * Register hooks on init.
   *
   * @since 4.4
   */
  public function register_hooks() {

    // Always add the common hooks.
    $this->register_hooks_common();

    // When in WordPress admin.
    if (is_admin()) {

      // Set context.
      $this->civicrm_context_set('admin');

      // Handle WordPress Admin context.
      $this->admin->register_hooks();

      // Enable shortcode modal.
      $this->modal->register_hooks();

      return;

    }

    // Go no further if CiviCRM not installed yet.
    if (!CIVICRM_INSTALLED) {
      return;
    }

    // Attempt to replace 'page' query arg with 'civiwp'.
    add_filter('request', [$this, 'maybe_replace_page_query_var']);

    // Add our query vars.
    add_filter('query_vars', [$this, 'query_vars']);

    // Delay everything else until query has been parsed.
    add_action('parse_query', [$this, 'register_hooks_front_end']);

  }

  /**
   * Register hooks for the front end.
   *
   * @since 5.6
   *
   * @param WP_Query $query The WP_Query instance (passed by reference).
   */
  public function register_hooks_front_end($query) {

    // Bail if $query is not the main loop.
    if (!$query->is_main_query()) {
      return;
    }

    // Bail if filters are suppressed on this query.
    if (TRUE == $query->get('suppress_filters')) {
      return;
    }

    // Prevent multiple calls.
    static $alreadyRegistered = FALSE;
    if ($alreadyRegistered) {
      return;
    }
    $alreadyRegistered = TRUE;

    // Redirect if old query var is present.
    if ('CiviCRM' == get_query_var('page') && 'CiviCRM' != get_query_var('civiwp')) {
      $redirect_url = remove_query_arg('page', FALSE);
      $redirect_url = add_query_arg('civiwp', 'CiviCRM', $redirect_url);
      wp_redirect($redirect_url, 301);
      exit();
    }

    // Store context.
    $this->civicrm_in_wordpress_set();

    // When embedded via wpBasePage or AJAX call.
    if ($this->civicrm_in_wordpress()) {

      /*
       * Directly output CiviCRM html only in a few cases and skip WordPress
       * templating:
       *
       * (a) when a snippet is set
       * (b) when there is an AJAX call
       * (c) for an iCal feed (unless 'html' is specified)
       * (d) for file download URLs
       */
      if (!$this->is_page_request()) {

        // Set context.
        $this->civicrm_context_set('nonpage');

        // Add core resources for front end.
        add_action('wp', [$this, 'front_end_page_load']);

        // Echo all output when WordPress has been set up but nothing has been rendered.
        add_action('wp', [$this, 'invoke']);
        return;

      }

      // Set context.
      $this->civicrm_context_set('basepage');

      // If we get here, we must be in a "wpBasePage" context.
      $this->basepage->register_hooks();
      return;

    }

    // Set context.
    $this->civicrm_context_set('shortcode');

    // That leaves us with handling shortcodes, should they exist.
    $this->shortcodes->register_hooks();

  }

  /**
   * Register hooks that must always be present.
   *
   * @since 4.4
   */
  public function register_hooks_common() {

    // Register user hooks.
    $this->users->register_hooks();

    // Register hooks for clean URLs.
    $this->register_hooks_clean_urls();

    if (!class_exists('CiviCRM_WP_REST\Plugin')) {

      // Set up REST API.
      CiviCRM_WP_REST\Autoloader::add_source($source_path = trailingslashit(CIVICRM_PLUGIN_DIR . 'wp-rest'));

      // Init REST API.
      new CiviCRM_WP_REST\Plugin();

    }

  }

  /**
   * Register hooks to handle Clean URLs.
   *
   * @since 5.12
   */
  public function register_hooks_clean_urls() {

    // Bail if CiviCRM is not installed.
    if (!CIVICRM_INSTALLED) {
      return;
    }

    // Bail if we can't initialize CiviCRM.
    if (!$this->initialize()) {
      return;
    }

    // Bail if CiviCRM is not using Clean URLs.
    if (!defined('CIVICRM_CLEANURL') || CIVICRM_CLEANURL !== 1) {
      return;
    }

    // Have we flushed rewrite rules?
    if (get_option('civicrm_rules_flushed') !== 'true') {

      // Apply custom rewrite rules, then flush rules afterwards.
      $this->rewrite_rules(TRUE);

      // Set a one-time-only option to flag that this has been done.
      add_option('civicrm_rules_flushed', 'true');

    }
    else {

      // Apply custom rewrite rules normally.
      $this->rewrite_rules();

    }

  }

  // ---------------------------------------------------------------------------
  // Construction of URLs
  // ---------------------------------------------------------------------------

  /**
   * Add our rewrite rules.
   *
   * @since 5.7
   *
   * @param bool $flush_rewrite_rules True if rules should be flushed, false otherwise.
   */
  public function rewrite_rules($flush_rewrite_rules = FALSE) {

    // Kick out if not CiviCRM.
    if (!$this->initialize()) {
      return;
    }

    // Get config.
    $config = CRM_Core_Config::singleton();

    // Get basepage object.
    $basepage = get_page_by_path($config->wpBasePage);

    // Sanity check.
    if (!is_object($basepage)) {
      return;
    }

    // Let's add rewrite rule when viewing the basepage.
    add_rewrite_rule(
      '^' . $config->wpBasePage . '/([^?]*)?',
      'index.php?page_id=' . $basepage->ID . '&civiwp=CiviCRM&q=civicrm%2F$matches[1]',
      'top'
    );

    // Maybe force flush.
    if ($flush_rewrite_rules) {
      flush_rewrite_rules();
    }

    /**
     * Broadcast the rewrite rules event.
     *
     * @since 5.7
     * @since 5.24 Added $basepage parameter.
     *
     * @param bool $flush_rewrite_rules True if rules flushed, false otherwise.
     * @param WP_Post $basepage The Basepage post object.
     */
    do_action('civicrm_after_rewrite_rules', $flush_rewrite_rules, $basepage);

  }

  /**
   * Add our query vars.
   *
   * @since 5.7
   *
   * @param array $query_vars The existing query vars.
   * @return array $query_vars The modified query vars.
   */
  public function query_vars($query_vars) {

    // Sanity check.
    if (!is_array($query_vars)) {
      $query_vars = [];
    }

    // Build our query vars.
    $civicrm_query_vars = [
      // URL query vars.
      'civiwp', 'q', 'reset', 'id', 'html', 'snippet',
      // Shortcode query vars.
      'action', 'mode', 'cid', 'gid', 'sid', 'cs', 'force',
    ];

    /**
     * Filter the default CiviCRM query vars.
     *
     * Use in combination with `civicrm_query_vars_assigned` action to ensure
     * that any other query vars are included in the assignment to the
     * super-global arrays.
     *
     * @since 5.7
     *
     * @param array $civicrm_query_vars The default set of query vars.
     * @return array $civicrm_query_vars The modified set of query vars.
     */
    $civicrm_query_vars = apply_filters('civicrm_query_vars', $civicrm_query_vars);

    // Now add them to WordPress.
    foreach ($civicrm_query_vars as $civicrm_query_var) {
      $query_vars[] = $civicrm_query_var;
    }

    return $query_vars;

  }

  /**
   * Filters the request right after WordPress has parsed it and replaces the
   * 'page' query variable with 'civiwp' if applicable.
   *
   * Prevents old URLs like example.org/civicrm/?page=CiviCRM&q=what/ever/path&reset=1
   * being redirected to example.org/civicrm/?civiwp=CiviCRM&q=what/ever/path&reset=1
   *
   * @see https://lab.civicrm.org/dev/wordpress/-/issues/49
   *
   * @since 5.26
   *
   * @param array $query_vars The existing query vars.
   * @return array $query_vars The modified query vars.
   */
  public function maybe_replace_page_query_var($query_vars) {

    $civi_query_arg = array_search('CiviCRM', $query_vars);

    // Bail if the query var is not 'page'.
    if (FALSE === $civi_query_arg || $civi_query_arg !== 'page') {
      return $query_vars;
    }

    unset($query_vars['page']);
    $query_vars['civiwp'] = 'CiviCRM';

    return $query_vars;

  }

  // ---------------------------------------------------------------------------
  // CiviCRM Initialisation
  // ---------------------------------------------------------------------------

  /**
   * Initialize CiviCRM.
   *
   * This method has been moved to "includes/civicrm.admin.php"
   *
   * @since 4.4
   * @since 5.33 Placeholder for backwards (and semantic) compatibility.
   *
   * @return bool True if CiviCRM is initialized, false otherwise.
   */
  public function initialize() {

    // Pass to method in admin class.
    return $this->admin->initialize();

  }

  // ---------------------------------------------------------------------------
  // Load Resources
  // ---------------------------------------------------------------------------

  /**
   * Perform necessary stuff prior to CiviCRM being loaded on the front end.
   *
   * This needs to be a method because it can then be hooked into WordPress at
   * the right time.
   *
   * @since 4.6
   */
  public function front_end_page_load() {

    static $frontend_loaded = FALSE;
    if ($frontend_loaded) {
      return;
    }

    // Add resources for front end.
    $this->add_core_resources(TRUE);

    // Merge CiviCRM's HTML header with the WordPress theme's header.
    add_action('wp_head', [$this, 'wp_head']);

    // Set flag so this only happens once.
    $frontend_loaded = TRUE;

  }

  /**
   * Load only the CiviCRM CSS.
   *
   * This is needed because $this->front_end_page_load() is only called when
   * there is a single CiviCRM entity present on a page or archive and, whilst
   * we don't want all the Javascript to load, we do want stylesheets.
   *
   * @since 4.6
   */
  public function front_end_css_load() {

    static $frontend_css_loaded = FALSE;
    if ($frontend_css_loaded) {
      return;
    }

    if (!$this->initialize()) {
      return;