Loading Instamojo Payment gateway SDK giving error

here is the SDK url https://github.com/Instamojo/instamojo-php

this page has the example I used in my CI 4 Application

below is my code

PHP Code:

$api = new \Instamojo\Instamojo::init('app', [
            "client_id" =>  'test_ssTbcIWGqmAQYEQUSu8tqyna6msQsQB4dEu',
            "client_secret" => 'test_Y7uuS7kjPgtK4Bi3R0RdWRZ0k9Hq67bhoeYw6Jsd2ZAYXNwUPNQo9vlGgsDAMoz1YjWvjDOcJdDlHIYGMJMFuo8XOsb9QfZH7fzNVvoG1EkGA4uG1GeLxjCcP8v'
        ], true); 


above code giving error :

Code:

"syntax error, unexpected 'init' (T_STRING), expecting variable (T_VARIABLE) or '$'"