resolver.register.php

<?php
$pkgName = 'SamplePackage';
$pkgNameLower = strtolower($pkgName);

if ($object->xpdo) {
  $modx =& $object->xpdo;
  $modelPath = $modx->getOption("{$pkgNameLower}.core_path",null,$modx->getOption('core_path')."components/{$pkgNameLower}/").'model/';

  switch ($options[xPDOTransport::PACKAGE_ACTION]) {
    case xPDOTransport::ACTION_INSTALL:
    case xPDOTransport::ACTION_UPGRADE:
      if ($modx instanceof modX) {
        $modx->addExtensionPackage($pkgName, "[[++core_path]]components/{$pkgNameLower}/model/", array(
          // 'serviceName' => $pkgName,
          // 'serviceClass' => $pkgName,
        ));
        $modx->log(xPDO::LOG_LEVEL_INFO, 'Adding ext package');
      } 
      break; 
        
    case xPDOTransport::ACTION_UNINSTALL:
      if ($modx instanceof modX) {
        $modx->removeExtensionPackage($pkgName);
      }
      break;
  }
}
return true;