Facebook图形api朋友邀请

I have managed to send and retrieve data from facebook for invitatin using

FB.ui({
            method: 'apprequests',
            to: sendto,
            message: 'Win Mega Prizes!',
            title: 'Enter in this contest!'
        },
        function (response) {   
           if (response && response.request_ids) {
               var requests = response.request_ids.join(',');
               alert(requests);
                    window.location.href = "http://www.rmyserver/index.php?invitations="+requests+"&contest_id="+c_id+"&page_id="+page_id+"&user="+from+"&g_id="+g_id+"&sendto="+sendto+"&single=1";         

            } else {
                alert('canceled');
            }

PHP

foreach($requests as $request_id) {
        // Get the request details using Graph API
       echo $request_content = json_decode(file_get_contents("https://graph.facebook.com/$request_id?$app_token"), TRUE);

But i want to use single user app request , as per docs i need to use TO: filed but this doesnt work, request is sent as well i get invitation id but php code used above returns false. Am i missing something

This works for me:

FB.ui({
            method:'apprequests',
            message:'I want you to open up your heart a little.',
            to:123456798,
            // filters:['app_non_users'], // commented: let users send notifications to app users too, probably a good idea to make them revisit?
            data:'' // send data what you would like to track, FB will send that back in the URL for us
            // @todo send google campaign parameters
        });

Moreover you are doing it wrong on PHP side, you would need to redirect the user to a URL where the invitation friend selector would be displayed. There is no way in my knowledge to directly send an invitation to users using PHP.

you can try direct url example given here https://developers.facebook.com/docs/reference/dialogs/requests/#frictionless_requests

that should work fine from php