WordPress: Export into theme all "Custom Post Type UI" post types and taxonomies

functions.php

/**
 * Saves post type and taxonomy data to JSON files in the theme directory.
 * @param array $data Array of post type data that was just saved.
 * Code originally provided by the author of the plugin
 */
function cptui_local_json( $data = array() ) {
  $theme_dir = get_stylesheet_directory();
  // Create our directory if it doesn't exist
  if ( ! is_dir( $theme_dir .= '/cptui-json' ) ) {
    mkdir( $theme_dir );
  }
  if ( array_key_exists( 'cpt_custom_post_type', $data ) ) {
    // Fetch all of our post types and encode into JSON.
    $cptui_post_types = get_option( 'cptui_post_types', array() );
    $content          = json_encode( $cptui_post_types );
    // Save the encoded JSON to a primary file holding all of them.
    file_put_contents( get_stylesheet_directory() . '/cptui-json/' . 'post_type_data.json', $content );
  }
  if ( array_key_exists( 'cpt_custom_tax', $data ) ) {
    // Fetch all of our taxonomies and encode into JSON.
    $cptui_taxonomies = get_option( 'cptui_taxonomies', array() );
    $content          = json_encode( $cptui_taxonomies );
    // Save the encoded JSON to a primary file holding all of them.
    file_put_contents( get_stylesheet_directory() . '/cptui-json/' . 'taxonomy_data.json', $content );
  }
}
add_action( 'cptui_after_update_post_type', __NAMESPACE__ . '\\cptui_local_json' );
add_action( 'cptui_after_update_taxonomy', __NAMESPACE__ . '\\cptui_local_json' );