Добавить пользователя с помощью API Joomla можно так:
require_once(JPATH_ROOT . DIRECTORY_SEPARATOR . 'components' . DIRECTORY_SEPARATOR . 'com_users' . DIRECTORY_SEPARATOR . 'models' . DIRECTORY_SEPARATOR . 'registration.php');
$user = new JUser;
$userData = array(
'name'=>'name',
'username'=>'username',
'password'=>'111111',
'password2'=>'111111',
'email'=>'email@pochta',
'id'=>0,
'groups'=>Array(2)
);
if (!$user->bind($userData)) {
$this->setError(JText::sprintf('COM_USERS_REGISTRATION_BIND_FAILED', $user->getError()));
return false;
}
if (!$user->save()) {
$this->setError(JText::sprintf('COM_USERS_REGISTRATION_SAVE_FAILED', $user->getError()));
return false;
}