Insert object to Google Cloud Storage at specific route using PHP - php

Question

I am amazed by the lack of information at the official documentation of Google Cloud Storage with PHP.
Here we go... I'm trying to manage bucket's uploads and downloads with Google APIs Client Library for PHP, but I can't find anywhere the way to specify to the API where I want to upload my files at google's bucket (I can only upload them at bucket's root).
Here's the code that I'm using for the upload (extracted from https://github.com/guillefd/Backup-manager-gcs/blob/master/application/libraries/Googlecloudstorage.php):
public function media_file_upload($file_path = null, $file_name = null) {
# init
$result = new stdClass();
$result->error = null;
$result->status = null;
$result->exception = null;
# timer
$result->starttime = microtime();
# init gcs api
$gso = new Google_Service_Storage_StorageObject();
$gso->setName($file_name);
$gso->setBucket($this->bucket);
$finfo = finfo_open(FILEINFO_MIME_TYPE);
$mimetype = finfo_file($finfo,$file_path);
$chunkSizeBytes = 1 * 1024 * 1024;
$this->client->setDefer(true);
$filetoupload = array(
'name'=>$file_name,
'uploadType'=>'resumable'
);
# service
$this->newStorageService();
$status = false;
# try
try {
$request = $this->storageService->objects->insert($this->bucket, $gso, $filetoupload);
$media = new Google_Http_MediaFileUpload($this->client, $request, $mimetype, null, true, $chunkSizeBytes);
$media->setFileSize(filesize($file_path));
$handle = fopen($file_path, "rb");
# loop chunks
while(!$status && !feof($handle)) {
$chunk = fread($handle, $chunkSizeBytes);
$status = $media->nextChunk($chunk);
}
fclose($handle);
$this->client->setDefer(false);
// $result->status = $status;
} catch(Exception $e) {
$result->error = true;
$result->status = 'Google Cloud Service upload failed';
$result->exception = $e;
}
# timer
$result->endtime = microtime();
$result->totaltime = $this->get_totaltime($result);
# verify response
$result->httpcode = http_response_code();
$result->error = isset($status->kind) && $status->kind==self::STORAGE_OBJECT ? false : true;
return $result;
}
The main question that I'm actually asking is: Is there a way to upload files to google's bucket at a specific route, using Google Cloud's PHP API?
Thanks!