isset: without or with?

[eluser]CroNiX[/eluser]
isset() will always be true in that case because this->input->post() will return boolean false if the variable does not exist, so it will ALWAYS be set (either FALSE, or a value). So you want to check with the === operator.

Code:

$q = $this->input->post('q');
if ($q !== FALSE) //variable existed

You don't want to use (!$q), because what if the post value was "0", which is a legitimate post value in a lot of forms.