Parsed: 131825

  public function add_rule( $selector ) {
    $selector = trim( $selector );

    // Bail early if there is no selector.
    if ( empty( $selector ) ) {
      return;
    }

    // Create the rule if it doesn't exist.
    if ( empty( $this->rules[ $selector ] ) ) {
      $this->rules[ $selector ] = new WP_Style_Engine_CSS_Rule( $selector );
    }

    return $this->rules[ $selector ];
  }