Is this overkill or good coding practice?

[cunoodle2]

Do you null set all variables at the top of your page?  I'm just trying to go over the top with my scripts as of recent to attempt to prevent any injections/bad things from happening.  Is this overkill or good coding practice...

 

<?php
###################################
#           NULL SET ALL VARIABLES                     #
###################################
$error = NULL;
$errornum = NULL;
$email = NULL;
$password = NULL;
$password2 = NULL;
$firstname = NULL;
$id = NULL;
$phone = NULL;

###################################
#             GET PASSED IN VALUES                     #
###################################
//these will all be sent in via the form submitted by the user
$firstname = isSet($_POST['firstname']) ? $_POST['firstname'] : NULL;
$password = isSet($_POST['password']) ? $_POST['password'] : NULL;
$password2 = isSet($_POST['password2']) ? $_POST['password2'] : NULL;
$email = isSet($_POST['email']) ? $_POST['email'] : NULL;

###################################
#                          CLEAN DATA                       #
###################################
$firstname = Clean($firstname);
$password = Clean($password);
$password2 = Clean($password2);
$email = Clean($email);
$error = Clean($error);
$errornum = Clean($errornum);

?>

[Cosizzle]

Hmm I would rather see that opposed to random variables thrown all over the place. I suppose for something simple its not needed, but I wouldnt call it 'bad practice'

[Ken2k7]

It's not like there's anything to Clean if the variable is null. The last two are unnecessary. But it's fine.

[allworknoplay]

Can you use isSet() like that?

 

Are the functions case-sensitive? I thought it was always just: isset()

[.josh]

if someone did manage to inject values into your variables beforehand, your new value assignments will overwrite it, regardless of whether it's NULL or $_POST['variable'] so that's really unnecessary. 

[cringe]

It's a great idea to always initialize all of your variables at the top of your script. If someone were to turn register globals on, you're more protected from "variable" injections.