Facebook application share to wall with JS variable

This is a problem caused by asynchronous events. The link_id is set in the callback function for the $.post. This callback function only runs once the POST request is complete - this could be a few seconds depending on the connection. But, the code after the $.post runs straight away - meaning the link_id is not set when you make the FB.ui call. Try this instead:

$.post( "https://host.com/save.php", { 'fb_id': userID, 'meth': 'get_db_ID' }, function(data) { link_id = data; console.log('from method' + link_id); FB.ui({ method: 'feed', name: 'My title for a link.', caption: ' ', description: 'My description', link: 'https://www.facebook.com/pages/Page-Test/1417010325197563?id=1417010325197563&sk=app_1413297985570561&app_data=u_id|'+link_id, picture: 'http://host.com/myimage.png' }, function(response) { console.log('publishStory response: ', response); }); });