Form not submitting data

Like kierownik said: $_POST (or $this->input->post()) will only have values if the inputs have names.
Best practice is to give the submit button a name also:

PHP Code:

<button type="submit" name="submit" class="hollow button submit">Submit</button> 


Then, in your controller:

PHP Code:

if ($this->input->post('submit')) {
   // handle form input
}
else {
   // show form
}