sending facebook notifications to multiple users

sending facebook notifications to multiple users

Ý have a facebook canvas application using php-sdk and i want to send
notifications to multiple users.
Using this code for sending notifications and its working.
$facebook->api('/USERID_1/notifications', 'POST', parameters);
But i want to send multiple ids so i try this code but its not working;
$facebook->api('/USERID_1,USERID_2,USERID_3/notifications', 'POST',
parameters);
is there any way to do that or its not possible?