Pasar Variables JSON a PHP

[superweb360]

en "data", quita las comillas y usa corchetes:

Código Javascript:

$.ajax({
type: "POST",
data: {nOpTipo:1,nOpCodigo:10},
url: "menu.php",
contentType: "application/json; charset=utf-8",
dataType: "json",
success: function (msg) {
}
})