错误:无法读取属性'；每个'；的未定义

我有一个JavaScript代码，它返回PHP的值并组装HTML表。给出的错误是不能读取每个未定义的属性。我看了好几次都没成功。他们能帮我一把吗？以下代码：

JavaScript:

function getListaItems(idprojeto) {
  //alert(idprojeto);
	jQuery.ajax({
		type: "POST",
		url: "get-lista-items.php?idprojeto=" + idprojeto,
		//data: dataEvento,
		dataType: 'json',
		success: function(resposta) {
			var str_html = '';
			$.each(resposta, function(){
				str_html = str_html + '<tr class="gradeA" id="' + this.id + '">' +
        '<td class="center"><input type="checkbox"  id="item[]" name="item[]" onchange="changeColor(' + this.id + ')" value="' + this.id + '" /></td>' +
        '<td class="center">' + this.descricao + '</td>' +
        '<td class="center">' + this.descCategoria + '</td>' +
        '<td class="center">' + this.descCaracteristica + '</td>' +
        '<td class="center">' + this.descMedida + '</td>' +
        '<td class="center"><input type="text" id="qtd' + this.id + '" style="width:80px"/></td>' +
        '</tr>';
			});
			document.getElementById("resultJs").innerHTML = str_html;
		}
	});
}

PHP:

<?php
	session_start();
	require_once("ProjectIncludes.php");
	$service = new ProjetoxItensService();
	$consulta = $service->getAll($_GET['idprojeto']);
	$retorno = json_encode($consulta);
	echo $retorno;
?>

谢谢，伙计们。