<?php
$url = 'adres_sklepu';
          $data = array('client_id' => 'login_użytkownika_z_web_api', 'client_secret' => 'password_użytkownika_z_web_api');
          $url_token = $url . '/webapi/rest/auth';

           $options = array(
               'http' => array(
                   'header'  => "Content-type: application/x-www-form-urlencoded",
                   'method'  => 'POST',
                   'content' => http_build_query($data),
               ),
           );
           $context  = stream_context_create($options);
           $result = (array) json_decode(file_get_contents($url_token, false, $context));
           #print_r($result);

           echo '<pre>';

           $token = $result['access_token'];
           echo $token;
           echo ' / ';
           echo $url;
           echo ' / ';
           echo $data['client_id'];
           echo ' / ';
           echo $data['client_secret'];

?>