Pre-populated inputs and validation

[eluser]codex[/eluser]
Hi,

I'm not sure how to implement this, so I could use a bit of advice. I have an 'edit profile' form which is prepopulated with the user's data. Some fields can't be left empty so his needs to be validated. For instance, a user can edit his name, but he can't completely erase it.

To validate I have to populate the input value like so (it's based on an own helper function, last option is 'value'):

Code:

<?php echo input_text("user_name", 20, "input_text", $this->validation->user_name)?>

But this way I can't populate the initial value with '$query[0]->user_name'. What can I do?

I thought of this:

Code:

<?php
if (!$this->input->post('user_name')) {
$name = $query[0]->user_first_name }
else { $name = $this->validation->user_name
}
echo input_text("user_first_name", 20, "input_text", $name)?>

But then I get an 'undefined variable' error. And something tells me I'm not thinking correctly ;-)