PHP en AJAX wat is hier fout aan? Weet niet of dit in PHP of JS thuishoord

$(function() {
	var lastChecked = '';
	
	function addResp(type, resp) {
		$("#post-reponses").append(
			"<div class='resp "+ type +"'>"+ resp +"</div>"
		);
	};
	
	function waitForResp() {
		$.ajax({
			type: "GET",
			url: "/responses?since="+lastChecked,
			async: true,
			cache: false,
			timeout:5000,
			success: function(data) {
				if (data.respons.length > 0) {
					lastChecked = data.lastChecked;
					data.respons.forEach(function(item) {
						addResp("respons", item.name);
					});
				}
                setTimeout(
                    waitForResp, 
                    1000 
                );
			}
		})
	};
	waitForResp();

});

	public function responsesAction()
	{
		if (empty($_GET['since']))
		{
			$responses	=	$this->blog->get_responses();
		}
		else
		{
			$responses	=	$this->blog->get_responses($_GET['since']);	
		}
		
		$data	=	$responses;
		header('Content-Type: application/json');
		
		echo json_encode(array(
			'respons'		=>	$data,
			'lastChecked' 	=> 	time()
		));
		
	}

	public function get_responces($response_date)
	{
		$sql	=	"SELECT *
		               FROM `post_responses`";
					  
		$params = array();
		if ($response_date)
		{
			$sql	.=	" WHERE `response_date` > :response_date";
			$params[':response_date'] = $response_date;	
		}
		
		$stmt = $this->pdo->prepare($sql . " ORDER BY `post_id` DESC");
		$stmt->execute($params);
			
		return $stmt->fetchAll(PDO::FETCH_ASSOC);	
	}