public function toArray()
  {
    $return = [];
    foreach ( $this as $property => $value ) {
      if ( '__' == substr( $property, 0, 2 ) || '' === $value || is_null( $value ) || ( is_array( $value ) && empty( $value ) ) ) {
        continue;
      }

      if ( in_array( $property, $this->functions ) && substr( $value, 0, 8 ) == 'function' ) {
        $value = "%{$property}%";
      }

      $return[ $property ] = $value;
    }

    return $return;
  }