you place the code snippet in the php script that is the action for the form, near the very top, so it is tested before the rest of your action script runs and processes the data, and exits at that point.

Many scripts use a foreach($_POST as $value) loop to check for blank fields in the data sent, or for characters likely to be used by a hacker (; — { and similar, see SQL Injection examples), so you’d have to have a little bit of code that tested each $value and if it was your hidden field, skip the check.

An approach of avoiding HTML form spam is using CSS. Non-human spammers usually fills out every input field in a form and submit it, and to overcome this kind of spam you must be able to differ between real human form submits and non-human spam. A tech…

// check if man or machine
if ($_POST['human'] == “”){
echo “Bad doggy. Sit bobo. Sit.”;
exit;}

in the form? Do you place it right after the “from action”?

I think it would be difficult very difficult for a bot to detect that another div that is positioned in front of the dummy input field.

I don’t think screen readers read the DOM tree, at all. They read the screen, literally. For example, Opera. If you hide an element with CSS, the screen reader doesn’t see it. Why should it, really?

I suspect this method is perfectly fine for screen readers, but I haven’t tested it.

#human {
top: -100px;
left: -100px;
}