I have a couple of email forms I have created that use PHP to email the
collected data to the appropriate recipient.

A concern has been raised by clients about the form being hacked by
spammers.

Is this likely to be a problem? If so what is the best way to stop it
happening. All I can think of is to maintain a log of, say, users ip
addresses and use this the limit the frequency with which the form can be
used.

Is there a better way?

Hamilton