A simple example on here:

server.php
<?php
class API {
   
    public function api($parameter = "", $option = "foo") {
          return $this->client_can_not_see($parameter);
    }
 
 
    public function doAdd($a = 0, $b = 0) {
          return $a+$b;
    }
   
    protected function client_can_not_see( $name ) {
      return "你好$name~";
    }
}

$service = new Yar_Server ( new API () );
$service->handle ();
?>
client.php
<?php
  $client = new Yar_Client("http://host/server.php");
  $result = $client->api("parameter");
  echo $result.'<hr>';
  echo $client->doAdd(10, 20);
?>