$GLOBALS in thema child

Ik heb een thema-child aangemaakt van thema ‘ReadLine’ met het bestand ‘functions.php’:

<?php
  add_action('wp_enqueue_scripts', 'child_enqueue_styles', 99);
  function child_enqueue_styles(){
    $parent_style = 'parent-style';
    wp_enqueue_style($parent_style,
                     get_template_directory_uri() . '/style.css');
    wp_enqueue_style('child-style',
                     get_stylesheet_directory_uri() . '/style.css',
                     array($parent_style));
  }
  if(get_stylesheet() !== get_template()){
    add_filter('pre_update_option_theme_mods_' . get_stylesheet(),
               function($value, $old_value){
                 update_option('theme_mods_' . get_template(), $value);
                 return $old_value; // prevent update to child theme mods
               }, 10, 2
              );
    add_filter('pre_option_theme_mods_' . get_stylesheet(),
               function($default){
                 return get_option('theme_mods_' . get_template(), $default);
               }
              );
  }
  /*----------------------------- Initialize globald data -------------------*/
  $GLOBALS['bbl_aaa'] = 'xxx';
  $GLOBALS['bbl_bbb'] = 'yyy';
  $GLOBALS['bbl_ccc'] = 'zzz';
  /*----------------------------- Allow web query parameters 'bkc' and 'chp' */
  function add_query_vars_filter($vars){
    $vars[] = 'bkc';
    $vars[] = 'chp';
    return $vars;
  }
  add_filter( 'query_vars', 'add_query_vars_filter' );
  get_query_var('bkc');
  get_query_var('chp');
?>

En het ‘XYZ PHP code’-bestand ‘bbl-bkx-001’:

<?php
/*=== File 'bbl-bkx-001.php' ===  Create bible book page (part 001) =========*/
/*------------------------------- Initialize data ---------------------------*/
echo   'Global data: '
     . $GLOBALS['bbl_aaa']
     . ', '
     . $GLOBALS['bbl-bbb']
     . ' and '
     . $GLOBALS['bbl_ccc'];
echo '<br>Query argument "bkc": '. get_query_var('bkc');
echo '<br>Query argument "chp": '. get_query_var('chp');
echo '<br>';
?>

Maar het werkt niet vanwege:

Warning: Undefined array key "bbl_aaa" in /...../wordpress/wp-content/plugins/insert-php-code-snippet/shortcode-handler.php(100) : eval()'d code on line 6
.......
Global data: , and
Query argument "bkc":
Query argument "chp": 

Waar zou ik iets verkeerds gedaan hebben?