public
function login($username, $password) {
  // fetch by username first
  $this - > db - > where('username', $username);
  $query = $this - > db - > get($this - > table);
  $result = $query - > row_array(); // get the row first

  if (!empty($result) && password_verify($password, $result['password'])) {
    // if this username exists, and the input password is verified using password_verify
    return $result;
  } else {
    return false;
  }
}