See also the Address response object.

PHP 
$address = $gateway->address()->find('a_customer_id', 'an_address_id');

If the address or customer can't be found, you'll receive a Braintree\Exception\NotFound exception.

Arguments
customerId required, string

A string value representing an existing customer in your Vault.
addressId required, string

The two-letter value for an address associated with a specific customer ID. The maximum number of addresses per customer is 50.