为标记添加唯一的信息窗口，并更新数据库以存储信息(谷歌地图api）

我目前正在编写一个旅游网站，该网站将允许用户点击地图，从而生成一个进入该位置的标记。从这里开始，我希望用户将信息窗口应用于特定的标记，其中包含详细信息，如国家、城市、持续时间、评论。然而，当我对此进行编码时，信息窗口将出现，但数据不是唯一的，用户输入和保存的数据在下一个标记上显示完全相同。例如，假设用户单击"爱尔兰"，当他们单击"英格兰"并编辑该标记时，该标记将包含所有爱尔兰信息。我如何使其独一无二？

这是我的HTML代码：

function initialize() {
  var latlng = new google.maps.LatLng(54.5, -7.0);
  var options = {
    zoom: 7,
    center: latlng,
    mapTypeId: google.maps.MapTypeId.ROADMAP
  }
  var map = new google.maps.Map(document.getElementById("map"), options);
  var html = "<table>" +
             "<tr><td>Country:</td> <td><input type='text' id='country'/> </td> </tr>" +
             "<tr><td>City:</td> <td><input type='text' id='city'/></td> </tr>" +
             "<tr><td>Duration:</td> <td><input type='text' id='duration'/></td> </tr>" +
             "<tr><td>Category:</td> <td><select id='category'>" +
                "<option value='city' SELECTED>City Break</option>" +
                "<option value='beach'>Beach Holiday</option>" +
                "<option value='romantic'>Romantic Holiday</option>" +
                "<option value='activity'>Activity Holiday</option>" +
                "<option value='site'>Site Seeing</option>" +
                "</select> </td></tr>" +
             "<tr><td></td><td><input type='button' value='Save & Close' onclick='saveData()'/></td></tr>";
infowindow = new google.maps.InfoWindow({
 content: html
});
google.maps.event.addListener(map, "click", function(event) {
    marker = new google.maps.Marker({
      position: event.latLng,
      map: map
    });
    google.maps.event.addListener(marker, "click", function() {
      infowindow.open(map, marker);
    });
});
}
function saveData() {
  var country = escape(document.getElementById("country").value);
  var duration = escape(document.getElementById("duration").value);
  var category = document.getElementById("category").value;
  var latlng = marker.getPosition();
  var url = "phpsqlinfo_addrow.php?country=" + country +  "&city" + city + "&duration=" + duration +
            "&category=" + category + "&lat=" + latlng.lat() + "&lng=" + latlng.lng();
  downloadUrl(url, function(data, responseCode) {
    if (responseCode == 200 && data.length >= 1) {
      infowindow.close();
      document.getElementById("message").innerHTML = "Location added.";
    }
  });
}
function downloadUrl(url, callback) {
  var request = window.ActiveXObject ?
      new ActiveXObject('Microsoft.XMLHTTP') :
      new XMLHttpRequest;
  request.onreadystatechange = function() {
    if (request.readyState == 4) {
      request.onreadystatechange = doNothing;
      callback(request.responseText, request.status);
    }
  };
  request.open('GET', url, true);
  request.send(null);
}
function doNothing() {}
</script>