php contact form - explanation required

Question

I was writing my personal website and thought about creation of contact form. Not a big deal....

But I would like to protect me somehow from auto generated requests by malicious scripts.

Captcha is not an option because it would discourage potential senders to contact me.

I tried to look how others handled this problem.

Among many unprotected forms I found pretty interesting example:

I can't explain the purpose of hidden input fields and I guess they have something to do with filtering malicious users from good users.

But. Am I right? How are they used?

Website where I picked this form website

Answer 1

If captcha is not an option you could use a honeypot .

This works for bots that are not able to interpret/render CSS. Here's how it works: Add an input field and hide it using CSS. Therefore a human would not fill out this field - but a machine probably would. After form-submission you check if the invisible field has been filled out - and if then you've probably identified a bot.