HTML/PHP Secure Contact Form?

Could anyone recommend a reasonably easy to implement, off-the-shelf-ish, cheapish (free!) PHP contact form I can plug into my website.

Discovered a few weeks back that some brightspark found an exploit in my (admittedly simple) home-rolled contact form so I’ve had to remove it. Tempted just to remove it all together and have just an email link but I do like a site with a contact form personally.