You may try the bellow code. Some times sequence may be important and implementing function(response) method directly instead of implementing fbCallback works for me.
FB.ui(
{
method: 'feed',
name: 'ManachiApp',
caption: 'I just want to share',
description: ('I just want to share on fb wall'),
link: 'https://apps.facebook.com/manachi/',
picture: 'http://manachi.herokuapp.com/images/logo_large.jpg'
},
function(response) {
if (response && response.post_id) {
alert('Post was published.');
} else {
alert('Post was not published.');
}
}
);