Google Cloud API - Application Default Credentials

You need to use putenv() (http://php.net/manual/en/function.putenv.php) instead of trying to use any of the methods you have used ($_ENV or $_SERVER).

Taken from https://github.com/google/google-api-php-client/blob/master/UPGRADING.md#google_auth_assertioncredentials-has-been-removed

// OR use environment variables (recommended)

putenv('GOOGLE_APPLICATION_CREDENTIALS=/path/to/service-account.json');
$client->useApplicationDefaultCredentials();

I agree with the above answer, but only want to describe if user getting error in php using nlp google:

<?php 

error_reporting(E_ALL);
ini_set('display_errors', 1);

# Includes the autoloader for libraries installed with composer
require __DIR__ . '/vendor/autoload.php';

# Imports the Google Cloud client library
use Google\Cloud\Language\LanguageClient;
putenv('GOOGLE_APPLICATION_CREDENTIALS=/home/sgupta/www/practise/nlp/google/cred.json'); //your path to file of cred
//$client->useApplicationDefaultCredentials();
# Your Google Cloud Platform project ID
$projectId = 'nlp-project-nname'; //your project name

# Instantiates a client
$language = new LanguageClient([
    'projectId' => $projectId
]);

# The text to analyze
$text = 'Sachin Tendulkar';



# Detects the sentiment of the text
$annotation = $language->analyzeSentiment($text);
$sentiment = $annotation->sentiment();
echo "<pre>";
print_r($annotation); die;

echo 'Text: ' . $text . '
Sentiment: ' . $sentiment['score'] . ', ' . $sentiment['magnitude'];
?>