Trying to figure out what posting comments through Facebook's graph API only sometimes works

AJAX

$(document).on('click', '.comment_submit', function(e) {
  	var $this = $(this);
		var post_id = $this.closest('.box').attr('data-post_id');
		var comment = $this.siblings('.comment_form').val();
		
		$.ajax({
			type: 'GET',
			url: 'interactions/facebook.interaction.php',
			data: {
				post_id: post_id,
				comment: comment,
				interaction: 'commenting'
			},
			//dataType: 'json',
			success: function(data) {
				console.log('true');
			},
			error: function(data) {
				console.log('error');
			}
		});

	});

PHP

$interaction = $_GET['interaction'];
$post_id = $_GET['post_id'];
$comment = $_GET['comment'];

if( $interaction === 'commenting' ) {
	$reply = $facebook->api('/' . $post_id . '/comments?message=' . $comment . '&access_token=' . $accessToken, 'post');
}