Forum:How does Gravekeeper's servants effect work

I was just wondering, because I have the original Gravekeeper's servant which states "Each time your opponent attacks with a monster, the opponent must send 1 card from the top of his/her Deck to the Graveyard."

While the new Gravekeeper's Servant says "Unless your opponent sends 1 card from the top of his/her deck to the Graveyard, he/she cannot declare an attack."

So, it got me wondering does my opponent need to send 1 card from the top of their deck to the graveyard in order to attack with all of their monsters or does my opponent need to send 1 Card from the top of their deck to the graveyard for each monster they attack with?