function check_file(filePath)	
{
	var request = HTTP.newRequest();
	request.open("POST", "check_file.php", false); // synchronous
	request.setRequestHeader("Content-Type", 
		"application/x-www-form-urlencoded");
	request.send(HTTP.encodeFormData({"filePath":filePath}));
	if(request.status == 200) {
		var response = request.responseText.replace(/^\s+|\s+$/g, "");
		return response;
	}
}