@bipin_1611 did you ever hear about Postman? Have a look at this link:
https://developer.squareup.com/docs/testing/postman
First set up your postman, then download squareup collection (all of the API endpoints already configured), then test it with postman so you are sure everything works as expected, then transfer that to Laravel.
It is much easier to troubleshoot that way.
Also the easiest way to access API in laravel is to use Http client:
https://laravel.com/docs/master/http-client#request-data
use Illuminate\Support\Facades\Http;
$response = Http::post('http://example.com/users', [
'name' => 'Steve',
'role' => 'Network Administrator',
]);
and then your json will be here:
$response->json();
Hope it helps!