Example

// Create new row in users table and return the unique id allocated
// if successful or false otherwise.
function newUser( $name ) {
  $database =& JFactory::getDBO();
 
  $user = new stdClass;
  $user->id = NULL;
  $user->name = $name;
 
  if (!$database->insertObject( '#__users', $user, 'id' )) {
    echo $database->stderr();
    return false;
  }
 
  return $user->id;
}
 
// Update an existing user record.
function updateUser( $id, $username ) {
  $database =& JFactory::getDBO();
 
  $user = new stdClass;
  $user->id = $id;
  $user->username = $username;
 
  if (!$database->updateObject( '#__users', $user, 'id' )) {
    echo $database->stderr();
    return false;
  }
 
}

$id = newUser( 'Linus Torvalds');
updateUser( $id, 'linus' );