code: public function setDDD( $ddd )
      {
          $ddd = preg_replace( '/^0+|\D/', '', $ddd );
  
          if (strlen( $ddd ) !== 2) {
              throw new InvalidArgumentException( sprintf( 'Invalid DDD (%s)', $ddd ) );
          }
  
          $this->ddd = $ddd;
  
          return $this;
      }
docs: @param  string $ddd
  
  @return $this