gistfile1.txt

class provisionServer {
  public static function evaluate($options) {
    return __CLASS__;
  }
}

class provisionPlatform extends provisionServer {
  public static function evaluate($options) {
    if (isset($options['root'])) {
      return __CLASS__;
    }
    parent::evaluate($options);
  }
}

class provisionSite extends provisionPlatform {
  public static function evaluate($options) {
    if (isset($options['uri'])) {
      return __CLASS__;
    }
    parent::evaluate($options);
  }
}

$class = provisionPlatform::evaluate(array('root' => 1));

$environment = new $class();
print_r($environment);