Right here below me 🙂
'My App Name',
'scope' => 'read/write',
'user_id' => 123,
'return_url' => 'http://app.com',
'callback_url' => 'https://app.com'
];
$query_string = http_build_query( $params );
echo $store_url . $endpoint . '?' . $query_string;
?>