Call to a member function on a non-object - fatal error

I've got text version of Advanced Poll and I can't get rid of this error:
Fatal error: Call to a member function on a non-object in /usr/local/apache2/htdocs/sonda.php on line 10

What is wrong?
<?php
// Important! You have to include it before your html code
include_once "http://mydomain.com/poll/poll_cookie.php";
?>

<html>
<body>
<?php
include_once "http://mydomain.com/poll/booth.php";
echo $php_poll->poll_process(3);
?>
</body>
</html>

I've got text version of Advanced Poll and I can't get rid of this error:
Fatal error: Call to a member function on a non-object in /usr/local/apache2/htdocs/sonda.php on line 10

Can you post a link to your page, sonda.php?

Not sure, but maybe you need register_globals turned on.