Comment Spamming stop comment spamming on my website

I have made a website and it has a simple comments feature on it so viewers can comment on my page. I have added a filter to filter out swear words but what is a way to stop people from spamming and ban them from the site for a period of time if they do spam my site. I do not require a login to view my site and was hoping to do this without forcing people to login. This may be more of a php question than mysql but I will have to use both to solve my problem i'm sure. Anyway, any advice would be much appreciated!