Order of Array Elements?
$data1 = array(
            'first_name'=>$this->input->post('first_name'),
            'last_name'=>$this->input->post('last_name'),
            'company'=>$this->input->post('company'),
            'email'=>$this->input->post('email'),
            'phone'=>$phonenum,
            'username'=>strtolower($this->input->post('first_name')) . ' ' . strtolower($this->input->post('last_name'))

unset($data1['email']);
unset($data1['username']);