HTML Forms Validation

srobertson

I want to validate HTML form data "prior to" submission and I'd prefer to do this in php.

I have some sample JavaScript but I wanted to avoid this so that the source code doesn't appear when viewed.

I know I can echo the form back to itself and validate the data then but to me this seems to be the long way around. Submitting the form then re-loading then re-loading then re-submitting.

Is there anyway to include a php validation function to check the forms data confirms to some pre-defined format in php.😕

ednark

I want to validate HTML form data "prior to" submission and I'd prefer to do this in php.

ok well you have to submit the form to let php get its hands on it...

you can simply choose to have php process or not process the data upon validation...

only javascript - or flash - or a java applet - or something actually in the browser can validate prior...

you want to look into these topics to help you validate

1) know how $POST and $GET work
2) know a little bit about regular expressions, and know the other pattern finding php functions like substr() and strstr(), that you can use to actually do the validation
3) know about sessions. you can have the form refill in values if the user gets them wrong by storing what was written in the $_SESSION between page loads
4) know the header('Location: url') trick if switching between pages

all these concepts are easily available in the manual...
i suggest if you are using windows to download the windows help file version of the documentatino for fastest access...

once you have reviewed these and you would like more specific advice... please post back

foamy

3) know about sessions. you can have the form refill in values if the user gets them wrong by storing what was written in the $_SESSION between page loads

Are sessions really necessary for this? Aren't all the form variables passed when the form is submitted? I usually just check for form completeness, then validate and if either step fails repopulate the form with echo statements and mark the problems in red.

I'm just a noob and my previous attempts at sessions have all failed miserably. Now, I'm working on a very basic shopping cart, so I guess it's about time to figure them out!

ednark

no sessions are not necessary for this

one trick is to have only one file and have it submit to itself...

if it sees submitted data it acts upon it
otherwise it prints the form...

if ( isset($_POST['the_form_data'] ) {
    process_data( $_POST['the_form_data'] );
} else {
    print_the_form();
}

some people have two files..

one that just does the form
one that just processes the form

if this is the case you can use the $_SESSION to remember things between pages, and can use the header() trick to jump from the processing page to either a success page, or back to the form...

but i must stress as you pointed out that neither is the correct way

whatever way you can get working is the correct way...

srobertson

ahh ok, that basically answered the question.

php is limited in what it can do with forms pre-submission....

I'd already worked out how to validate post submission which really wasn't the problem. It's just an non-vulcan process to do it the long way round it just takes extra time to load and re-load the forms.

🆒