Re: When are Form Variables Null?

Al, This depends entirely on your browser actually, as it is the one sending form variables back to the server in a POST request. Luckily, browsers are very consistent with how they handle this. :) Off the top of my head (I might be forgetting some form field types): text fields - always set drop downs - always set radio buttons - will not be set if no radio box was selected checkboxes - will not be set if no checkbox was checked The best way to test this (always best to make sure rather than trust a stranger on a mailing list, heh) would be to create a page with every type of form field you can think of and submit it to a PHP page where you loop through and output every variable in $_POST. As for the functions you mention, is_null() checks to see if the variable has a null value, which I believe is never the case for form fields (someone correct me if I'm wrong). The function empty() is the same check as ( == "") and will be true for text fields where the user did not enter anything. The isset() function will let you know if a variable exists at all. For the case of a single checkbox in a form fields, the variable will be set if it was checked, and it will not be set if the box was not checked. Chris Al Baker wrote:

Hi, I've been wondering the behavior of browsers and POST submissions.. basically I'd like to know the behavior of: is_null(), empty(), and isset(). I've found that sometimes when an item is not filled out, the variable is still set on the subsequent page, like $_POST['var'] = ""; What does everyone use to see if forms were submitted correctly? I built my own function: function form_exists($variable) { if (strlen($variable) < 1) { return false; } else { return true; } } It was the only apparent way I could know *for sure* that independent of the browser, I knew what the heck was being submitted. Thoughts? Thanks, Al