Unable to connect to your database server using the provided settings.

PHP Code:
public function verversCampagne(){

  
        $config['hostname'] = 'secret';
        $config['username'] = 'secret';
        $config['password'] = 'secret';
        $config['database'] = 'dbname';
        $config['dbdriver'] = 'sqlsrv';
        $config['dbprefix'] = '';
        $config['pconnect'] = TRUE;
        $config['db_debug'] = TRUE;
        $config['cache_on'] = FALSE;
        $config['cachedir'] = '';
        $config['char_set'] = 'utf8';
        $config['dbcollat'] = 'utf8_general_ci';

        $this->db = $this->load->database($config, true);

        $search = $this->input->post('campagne');

        $dropdown_data['search'] = $search;

        $query = $this->db->query("SELECT Campagne FROM project WHERE campagne in ('$search')");

        $databasenaam = $query->row();

        if($query->num_rows() > 0)
        {
            return $databasenaam->Campagne;
        } else {
            return $databasenaam;
        } 
    }