[Can't use method return value in write context] for checking a form variable

[eluser]sahanlak[/eluser]
This function is within a controller,

Code:

function settings()
        {
            $data['members']=TRUE;

            $this->load->model('user_model');
            $user=$this->user_model;
            /*-- Update Settings --*/
            
            if( isset($this->input->post('update')) )
            {
                $name=$this->input->post('name');
                $pp_email=$this->input->post('pp_email');
                $country=$this->input->post('country');
                
                $user->update_user($name, $pp_email, $country);
            }
            
                        
            $data['action']='settings';
            $data['user_data']=$user->get_user();
            
            $this->load->view('members/home', $data);
        }

I'm getting an error @ [if( isset($this->input->post('update')) )]

Why?

Erro:

Can't use method return value in write context