How to use JSON key instead of P12 in Google Spreadsheet Authentication with PHP?

Here is the solution I found.

For P12 Key
Normally, we use the following code to generate a token.

public static function getToken()    {        $key = file_get_contents( APPLICATION_DIR.'/'.APPLICATION_GOOGLE_CLIENT_KEY_FILE);        $cred = new Google_Auth_AssertionCredentials(            APPLICATION_GOOGLE_CLIENT_EMAIL,            array('https://spreadsheets.google.com/feeds'),            $key        );        $client = new Google_Client();        $client->setAssertionCredentials($cred);        if (!$client->getAuth()->isAccessTokenExpired()) {            return false;        }        else {            $client->getAuth()->refreshTokenWithAssertion($cred);        }        $service_token = json_decode($client->getAccessToken());        return $service_token->access_token;    }

For JSON Key
But now we don't have P12 key, we have a JSON key, so I just made some changes in the above code, please take a look below:

public static function getToken()    {        $key = APPLICATION_DIR.'/'.APPLICATION_GOOGLE_CLIENT_KEY_FILE;        $data = json_decode(file_get_contents($key));    // here i decoded the json         if (isset($data->type) && $data->type == 'service_account') {            $cred = new Google_Auth_AssertionCredentials(                APPLICATION_GOOGLE_CLIENT_EMAIL,    // it's the client email                array('https://spreadsheets.google.com/feeds'),   // it's google spreadsheet scope                $data->private_key         // here is the private key            );         }        $client = new Google_Client();        $client->setAssertionCredentials($cred);        if (!$client->getAuth()->isAccessTokenExpired()) {            return false;        }        else {            $client->getAuth()->refreshTokenWithAssertion($cred);        }        $service_token = json_decode($client->getAccessToken());        return $service_token->access_token;    }

Access token will only be valid 1 hour and is sent as decoded json. So you probably have to decode it first.

$token = json_decode($client->getAccessToken());$serviceRequest = new DefaultServiceRequest($token->access_token);ServiceRequestFactory::setInstance($serviceRequest);

Using p12 key should work fine then.

session_start();define('GOOGLE_CLIENT_ID','');define('GOOGLE_CLIENT_EMAIL','');define('GOOGLE_SPREADSHEETS_SCOPE','https://spreadsheets.google.com/feeds');define('GOOGLE_APPLICATION_NAME','whatever');define('GOOGLE_KEY_FILE','xxxxxxxxxxxxxx.p12'); // pass for key: notasecretfunction getToken(){    $client = new Google_Client();    $client->setApplicationName(GOOGLE_APPLICATION_NAME);    $client->setClientId(GOOGLE_CLIENT_ID);    $key = file_get_contents(GOOGLE_KEY_FILE);    $cred = new Google_Auth_AssertionCredentials(        GOOGLE_CLIENT_EMAIL,        array(GOOGLE_SPREADSHEETS_SCOPE),        $key    );    $client->setAssertionCredentials($cred);    if($client->getAuth()->isAccessTokenExpired()) {        $client->getAuth()->refreshTokenWithAssertion($cred);    }    $service_token = json_decode($client->getAccessToken());    return $service_token->access_token;}require("vendor/autoload.php");use Google\Spreadsheet\DefaultServiceRequest;use Google\Spreadsheet\ServiceRequestFactory;$_SESSION['access_token']=getToken();$serviceRequest = new Google\Spreadsheet\DefaultServiceRequest($_SESSION['access_token']);Google\Spreadsheet\ServiceRequestFactory::setInstance($serviceRequest);$spreadsheetService = new Google\Spreadsheet\SpreadsheetService();$spreadsheetFeed = $spreadsheetService->getSpreadsheets();