Взять координаты центра карты из input

<?$row['coordinates']="30.518474,50.468465";?>

<input type="text" maxlength="50" name="coordinates" id="coordinates" value="<?echo $row['coordinates']?>"/>

<script type="text/javascript">

window.onload = function () {
                    var coord = $("#coordinates").val();  
                    var map = new YMaps.Map(document.getElementById("YMapsID"));
                    map.setCenter(new YMaps.GeoPoint(coord ), 15);
                    map.addControl(new YMaps.Zoom());
                                        
                    var s = new YMaps.Style();
                    s.iconStyle = new YMaps.IconStyle();
                    s.iconStyle.href = "/image/metka.png";
                    s.iconStyle.size = new YMaps.Point(40, 38);
                    s.iconStyle.offset = new YMaps.Point(-15, -33);
            
                    var placemark = new YMaps.Placemark(new YMaps.GeoPoint(coord ), {style: s, draggable: true});
                    map.addOverlay(placemark); 
                   
                    YMaps.Events.observe(placemark, placemark.Events.Drag, function (mEvent) {
                           $("#coordinates").val(mEvent.getGeoPoint().toString());
                    });
                }

</script>