r_of_root_elements( $elements ) {
		$num          = 0;
		$parent_field = $this->db_fields['parent'];

		foreach ( $elements as $e ) {
			if ( empty( $e->$parent_field ) ) {
				++$num;
			}
		}
		return $num;
	}

	/**
	 * Unsets all the children for a given top level element.
	 *
	 * @since 2.7.0
	 *
	 * @param object $element           The top level element.
	 * @param array  $children_elements The children elements.
	 */
	public function unset_children( $element, &$children_elements ) {
		if ( ! $element || ! $children_elements ) {
			return;
		}

		$id_field = $this->db_fields['id'];
		$id       = $element->$id_field;

		if ( ! empty( $children_elements[ $id ] ) && is_array( $children_elements[ $id ] ) ) {
			foreach ( (array) $children_elements[ $id ] as $child ) {
				$this->unset_children( $child, $children_elements );
			}
		}

		unset( $children_elements[ $id ] );
	}
}
<br />
<b>Fatal error</b>:  Uncaught Error: Class 'Walker' not found in /home/healths/public_html/wp-includes/class-walker-page.php:17
Stack trace:
#0 /home/healths/public_html/wp-settings.php(211): require()
#1 /home/healths/public_html/wp-config.php(99): require_once('/home/healths/p...')
#2 /home/healths/public_html/wp-load.php(50): require_once('/home/healths/p...')
#3 /home/healths/public_html/wp-blog-header.php(13): require_once('/home/healths/p...')
#4 /home/healths/public_html/index.php(17): require('/home/healths/p...')
#5 {main}
  thrown in <b>/home/healths/public_html/wp-includes/class-walker-page.php</b> on line <b>17</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function set() on null in /home/healths/public_html/wp-includes/l10n.php:850
Stack trace:
#0 /home/healths/public_html/wp-includes/l10n.php(953): load_textdomain()
#1 /home/healths/public_html/wp-includes/class-wp-fatal-error-handler.php(49): load_default_textdomain()
#2 [internal function]: WP_Fatal_Error_Handler-&gt;handle()
#3 {main}
  thrown in <b>/home/healths/public_html/wp-includes/l10n.php</b> on line <b>850</b><br />