Add Tester to play Track with Php

Trying to add programatically tester email’s to google play track for intern Test.
How can i do that with Php?
I tried to post new tester unsuccessfully

<?php 
        $headers = array();
        $body    = array(  
                    'grant_type'    => 'authorization_code',
                    'code'          => $code."#",
                    'client_id'     => $client_id,
                    'client_secret' => $client_secret,
                    'redirect_uri'  => "https://website.com/callback",
        );

        $response = UnirestRequest::post("https://accounts.google.com/o/oauth2/token", $headers, $body);

        var_dump($response->body);

?>