trying to cal a php page within jquery but no data returned

[Virangya]

hi ,
this is my code. i want to return data using a php page after processing a query within it.

$.post('check_booked.php', { room:roomv, srtdate:sdatev, eddate:sdatev},
       	function(data){
		alert( data);
    });

before completing php page i test using online code which returned nothing.. i don't know what wrong,
as i have understood anything within that php page eg: html code should be returned by this code. this is the test code i used and which didn't return anything.

$.post("check_booked.php", function(data) {
	alert("Data Loaded: " + data);
	 });

and i have

<h1>hi</h1>

in my php page

Please help me solve this much appreciate help..!