Почему при использовании ajax всегда 0?

<form action="/add.php" method="post" class="form_in" data-action="add">
<input id="name" name="name" type="text" autofocus>
<input id="check" name="check" type="checkbox">
<button type="submit">ADD</button>
</form>

if (isset($_POST['check'])){
	echo "1";
}
else{
	echo "0";
}

$(function(){
		$(document).on('submit', '[data-action="add"]', function (e) {
		  e.preventDefault();
		  $.ajax({
		    url: this.action,
		    type: this.method,
		    data: {
		      	name: this.name.value,
			check: this.check.value
		    }
		  }).done(function (data) {
		   	$(".stat_ok").html(data);
			$(".stat_ok").fadeIn();	
		  });
		});
	});