谷歌地图没有显示在PHP页面中

Question

我正在我的网页上实施谷歌地图。点击index.php中的更新按钮后，我显示一个对话框，其中包含谷歌地图供用户查找其位置。地图显示不正确。请帮帮我！

我的js：

> [2,4,6,8,10,12,14,16,18,20]

HTML

if(!window.google||!window.google.maps){
var script = document.createElement('script');
script.type = 'text/javascript';
script.src = 'https://maps.googleapis.com/maps/api/js?v=3&' +
    'callback=initialize';
document.body.appendChild(script);
}
else{
  initialize();
}


 <script>
    var directionsDisplay,
    directionsService,
    map;

    function initialize() {
         var directionsService = new google.maps.DirectionsService();
        directionsDisplay = new google.maps.DirectionsRenderer();
        var chicago = new google.maps.LatLng(51.508742,-0.120850);
        var mapOptions = { zoom:3, mapTypeId: google.maps.MapTypeId.ROADMAP, center: chicago }
        map = new google.maps.Map(document.getElementById("googlemap"), mapOptions);
        var marker=new google.maps.Marker({
           position:chicago,
  });
        directionsDisplay.setMap(map);
}

输出：