Retrieve customer data using the API using PHP

I would like to retrieve customer data in a list of orders that I have. Ando something lost in how to recover the detail of each element that forms the XML from the xlink ...

The current structure that I have in the XML that returns to me is:

<?xml version="1.0" encoding="UTF-8"?>
<prestashop xmlns:xlink="http://www.w3.org/1999/xlink">
  <orders>
    <order>
      <id><![CDATA[1]]></id>
      <id_address_delivery xlink:href="https://direccionweb.com/api/addresses/1"><![CDATA[1]]></id_address_delivery>
      <id_cart xlink:href="https://direccionweb.com/api/carts/1"><![CDATA[1]]></id_cart>
      <id_customer xlink:href="https://direccionweb.com/api/customers/1"><![CDATA[1]]></id_customer>
      <id_carrier xlink:href="https://direccionweb.com/api/carriers/1"><![CDATA[1]]></id_carrier>
      <current_state xlink:href="https://direccionweb.com/api/order_states/1"><![CDATA[1]]></current_state>
    </order>
    <order>
      <id><![CDATA[2]]></id>
      <id_address_delivery xlink:href="https://direccionweb.com/api/addresses/2"><![CDATA[2]]></id_address_delivery>
      <id_cart xlink:href="https://direccionweb.com/api/carts/2"><![CDATA[2]]></id_cart>
      <id_customer xlink:href="https://direccionweb.com/api/customers/2"><![CDATA[2]]></id_customer>
      <id_carrier xlink:href="https://direccionweb.com/api/carriers/1"><![CDATA[1]]></id_carrier>
      <current_state xlink:href="https://direccionweb.com/api/order_states/1"><![CDATA[1]]></current_state>
    </order>
   </orders>
 </prestashop>

And what I want is, among other things, to show the client's data (name, surnames and others).

I know that the client 1 data will be at: link That of the client 2 : link

and so on. But how do I do it to have all the data together? Should I make multiple calls? How exactly?

Currently, I get to paint the client's id. So like this:

try {
// creating web service access
$webService = new PrestaShopWebservice(PS_SHOP_PATH, PS_WS_AUTH_KEY, DEBUG);

// call to retrieve all customers
$xml = $webService->get(array(
                            'resource'  => 'orders',
                            'display'   => '[id, id_address_delivery, id_cart, id_carrier, id_customer, current_state]'
                        ));
$resources = $xml->orders->order;
foreach($resources as $resource) 
    echo '<label>Pedido</label><p>' . $resource->children()->id . '</p>' . 
         '<label>Cliente<label><p>' . $resource->children()->id_customer . '</p>';
}
catch (PrestaShopWebserviceException $ex) {
    // Shows a message related to the error
    echo 'Other error: <br />' . $ex->getMessage();
}