What's the proper way to check form vals

[Anon]

I've got a form that asks for some user input. I don't want the php code on the form to execute until the values have been filled out and the form submitted.
What's the best way to do this? I was checking for null values in the fields but I still get this error when the form first loads (before values are entered):

Notice: Undefined index: tbname in D:\wwwroot\secured\tablepick.php on line 82

Where 'tbname' is one of the field names. I get a notice like this for each field value I'm trying to read.

I tried using $POST['tbname'] and placing it in a variable then checking for a value. But I'm assuming it's not working because $POST is empty. I'm just not sure what the best way to check for this kind of stuff would be.

Also, is there a way to execute some php code when a user clicks a button without submitting a form?

[Anon]

To answer your last question first: No. For that job you'll need to write some Javascript.
Even if you do that, though, you will still need to check again after the submission in case the Javascript wasn't executed.

you can fill in default values for the $_POST[] variables if they're null with something like

if(!isset($POST['tbname'])) $POST['tbname']='';

[Anon]

Ahh yes, isset(). I didn't think to use that. Thanks, I'll give it a shot.

So, the only time php will execute is when the form is loaded (or submitted which really is sort of the same thing if you are just directing it back to the same form)?

I'm just trying to get a handle on when I can cause php scripts to do something. Can I somehow call a php function from javascript without just loading a whole page?

[mithril]

No, JavaScript is executed by the browser. PHP is executed by the server. The only way to execute PHP code is to submit a request to the server, in this case a form submission. You can write validation routines in JavaScript to remove the need to submit each time, but as Grumbler said you'll still need to write PHP validations to catch instances where the browser hasn't executed the JavaScript.

-geoff