Have javascript right, but need to pass variable with ajax, GIVING REP!

Have javascript right, but need to pass variable with ajax, WILL GIVE REP!

function showBox() {
var selectBox = document.getElementById("store").value;
	if (selectBox == 'N') {
	document.getElementById("penyard").style.display="none";
	}else{
	document.getElementById("penyard").style.display="block";
		}
}

Code (markup):

so how do I pull the value of selectBox to php without refreshing the page.
penyard needs the value of selectBox to know what to display.

 

data = 'store='+selectBox;
$.post("page.php",data,function(response, status, xhr)
{
    if (status == "error")
    {
        alert("Error:"+ xhr.status + " " + xhr.statusText);
    } else {
        Alert("sucess");
    }
});

Code (markup):

On page.php, you will get the value $_POST['store'];