Cannot upload file to google drive using service account - google-drive-api

Question

I am trying to use service account of goolge drive api to upload the file to 'my' central Google Drive.
I get the sample code from the Google drive API, however, when I run the code, exactly, when insert file into drive using Google_DriveService, the Google chrome show that "This webpage is not available".
Here is my php code:
<?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";
session_start();
/**
* Build and returns a Drive service object authorized with the service accounts.
*
* #return Google_DriveService service object.
*/
function buildService() {
$DRIVE_SCOPE = 'https://www.googleapis.com/auth/drive';
$SERVICE_ACCOUNT_EMAIL = '<email>#developer.gserviceaccount.com';
$SERVICE_ACCOUNT_PKCS12_FILE_PATH = '<filename>.p12';
$key = file_get_contents($SERVICE_ACCOUNT_PKCS12_FILE_PATH);
$auth = new Google_AssertionCredentials(
$SERVICE_ACCOUNT_EMAIL,
array($DRIVE_SCOPE),
$key);
$client = new Google_Client();
$client->setUseObjects(true);
$client->setAssertionCredentials($auth);
return new Google_DriveService($client);
}
function uploadFile($service, $mime, $src) {
//Insert a file
$file = new Google_DriveFile();
$file->setMimeType($mime);
$data = file_get_contents($src);
try {
//ERROR HERE: cannot insert (upload) file
$createdFile = $service->files->insert($file,
array(
'data' => $data,
'mimeType' => $mime,
'convert' => true,
)
);
return $createdFile;
} catch (Exception $e) {
print "An error occurred: " . $e->getMessage();
}
}
//test upload file to server
$service =buildService();
$mineType = "application/vnd.openxmlformats-officedocument.wordprocessingml.document";
$path = "toupload.docx";
$file = uploadFile($service,$mineType, $path);
?>