Stripe Q24。After attaching the source to the customer object, how do I check from the customer object?

$customer1 = \Stripe\Customer::create([

    "description" => "test",

    'email' => 'a@example.com',

]);

$customerObj = \Stripe\Customer::retrieve($customer1->id);

$sourceObj = $customer->sources->create(["source" => 'src_xxxx']);

The source object has been created. I can understand this.

I can not understand where in the Customer object the source object was created.

How can I check the source object created above from the Customer object?

var_export($customer->sources->source);

\Stripe\Stripe::setApiKey("sk_test_xxxx");



$customer = \Stripe\Customer::retrieve('cus_EhrAhwK7W4OB41');



foreach($customer->sources->data as $key => $val){

  echo $val->id."<br>";

}