Understanding FB Page IDs from API - php

Question

I'm working with the the fb page and I have pulled posts from a use using:
$fbapp = PVConfiguration::getConfiguration('afbapp');
$facebook = new Facebook( array('appId' => $fbapp -> app_id, 'secret' => $fbapp -> app_secret, 'cookie' => true ));
$facebook->api( $this -> fb_page_id . '/feed');
Now a sample result looks something like this:
[0] => Array
(
[id] => 311007125672751_315405295232910
[from] => Array
(
[category] => Retail and consumer merchandise
[name] => Example Demos
[id] => 311007125672751
)
[story] => Phonefare Demos added a new photo.
[story_tags] => Array
(
[0] => Array
(
[0] => Array
(
[id] => 311007125672751
[name] => Example Demos
[offset] => 0
[length] => 15
[type] => page
)
)
)
[picture] => https://fbcdn-photos-e-a.akamaihd.net/hphotos-ak-ash2/576447_315405255232904_1958203550_s.jpg
[link] => https://www.facebook.com/photo.php?fbid=315405255232904&set=a.315405251899571.62826.311007125672717&type=1&relevant_count=1
[icon] => https://static.xx.fbcdn.net/rsrc.php/v2/yz/r/StEh3RhPvjk.gif
[actions] => Array
(
[0] => Array
(
[name] => Comment
[link] => https://www.facebook.com/311007125672751/posts/315405295232910
)
[1] => Array
(
[name] => Like
[link] => https://www.facebook.com/311007125672751/posts/315405295232910
)
)
[privacy] => Array
(
[description] => Public
[value] => EVERYONE
[friends] =>
[networks] =>
[allow] =>
[deny] =>
)
[type] => photo
[status_type] => added_photos
[object_id] => 315405255232904
[created_time] => 2012-12-21T15:04:37+0000
[updated_time] => 2012-12-21T15:04:37+0000
[shares] => Array
(
[count] => 2
)
[likes] => Array
(
[data] => Array
(
[0] => Array
(
[id] => 45608554
[name] => Michele A
)
)
[paging] => Array
(
[cursors] => Array
(
[after] => NDU2MDg1NjY=
[before] => NDU2MDg1NjY=
)
)
)
)
My greatest point of confusion is this. I want to store the post in the database as a bigint. But the return id is
311007125672751_315405295232910
, and I'm guessing its two IDS. So which ID should I be storing in the database to reference later? What are both IDs for? Is there a fundamental flaw for breaking the IDS apart to start them as BigInts/UUIDs?