How to browse files from projects google drive - php

Question

i have created project in google console with service type credentials. I have downloaded p12 key file, and then wrote sample code for inserting file to test it:
<?php
require_once 'google-api-php-client/src/Google_Client.php';
require_once 'google-api-php-client/src/contrib/Google_DriveService.php';
require_once "google-api-php-client/src/contrib/Google_Oauth2Service.php";
$scopes = array('https://www.googleapis.com/auth/drive');
$accountEmail = 'SECRET';
$accountP12FilePath = './key.p12';
$key = file_get_contents($accountP12FilePath);
$auth = new Google_AssertionCredentials($accountEmail, $scopes, $key);
$client = new Google_Client();
$client->setUseObjects(true);
$client->setAssertionCredentials($auth);
$service = new Google_DriveService($client);
$file = new Google_DriveFile();
$file->setTitle('Test Title');
$file->setDescription('test description');
$parent = new Google_ParentReference();
$file->setParents(array($parent));
$createdFile = $service->files->insert($file, array(
'data' => 'test data',
'mimeType' => 'text/plain'
));
var_dump($createdFile);
?>
It dumps Google_DriveFile object with many urls. Some of them, like 'downloadUrl', returns 401 Unauthorized error. When I tried 'alternateLink' it showed google drive page with information that i need access, and buttons to request access and to switch account.
It also said that Im currently logged on my account, that was beeing used to create project, and that is visible on Permissions page of the project on the google console page.
How can I access drive that belongs to the project I used in the script ?

Answer 1

Finally found solution, it was missing permissions on file. Its worth to note that passing permission object to the $file object (before insertion) didn't work. I had to insert permission by passing already created file ID and permission object to the $service->permissions->insert method, just like that:
$permission = new Google_Permission();
$permission->setValue('PERSONAL.ACCOUNT#gmail.com');
$permission->setType('user');
$permission->setRole('writer');
$service->permissions->insert($createdFile->getId(), $permission);
Still I wasn't able to actually edit this file. When I opened file with URL
$createdFile->getAlternateLink();
Then I had to reopen that file with google docs. That copied file to my personal account and then I could only edit only that copy of a file, not a base file itself.
I dont know if there is a way to make that files truly editable, but I moved to the dropbox, as google drive API and its documentation SUX.