You need to actually
send the request. $cabecera merely contains a description of what you'd
eventually be sending (command, arguments, etc.).
To send a request, you use $client, and it's sendSync() or sendAsync() method in particular, and give it the request, which will
then be sent.
Also, "return" works within a function/method or an included file. If you want to print it on screen directly, you'd want to use "echo" insted.
E.g.
php code
<?php
use PEAR2\Net\RouterOS;
// require_once 'pear2\src\PEAR2\Autoload.php';
require_once 'PEAR2_Net_RouterOS-1.0.0b4.phar';
$client = new RouterOS\Client('xx.xxx.xx.xxx', 'victor', 'xxxxx');
$cabecera = new RouterOS\Request('/system/identity/print');
$cabecera_result = $client->sendSync($cabecera);
echo $cabecera_result('name');
?>