将PHP变量传递给Google Maps API

When a user signs up to my application (college project), they are asked for their address. I convert this address to latitude and longitude and then store it in my database.

I access the latitude and longitude like so:

<?php
    require '../connect.php';
    session_start();
    $_SESSION['username'];

    $sql = "SELECT latitude, longitude FROM userinformation WHERE username = '". $_SESSION['username']. "'";
$result = $db->query($sql);

    if($result->num_rows > 0){
        while($row = $result->fetch_assoc()){
            $lat = $row["latitude"];
            $lng = $row["longitude"];
            echo $lat;
            echo $lng;

        }
    }
?>

I then try to pass the $lat and $lng variable into the Maps API script like so:

function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 13,
    center: {lat: '<?php echo $lat;?>', lng: '<?php echo $lng;?>'}
  });

  marker = new google.maps.Marker({
    map: map,
    draggable: true,
    animation: google.maps.Animation.DROP,
    position: {lat: '<?php echo $lat;?>', lng: '<?php echo $lng;?>'}
  });
  marker.addListener('click', toggleBounce);
}

This gives me the following page:

I have also tried converted the PHP variables to JS:

var js_variable  = '<?php echo $lat;?>';
document.write(js_variable);
var js_variable1  = '<?php echo $lng;?>';
document.write(js_variable1);

I then pass in the JS variables instead of the PHP variables, however the output is still the same. What would be the correct way to pass a variable as lat/lng instead of a hardcoded value:

center: {lat: 59.325, lng: 18.070}
position: {lat: 59.327, lng: 18.067}

When I replace the values in the fiddle with strings {lat: '30.365273', lng: '-81.699600'}, I get a javascript error reported by the API: Assertion failed: InvalidValueError: setPosition: not a LatLng or LatLngLiteral: in property lat: not a number.

If I use parseFloat on those strings, it works:

code snippet:

function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 13,
    center: {
      lat: parseFloat('30.365273'),
      lng: parseFloat('-81.699600')
    }
  });

  marker = new google.maps.Marker({
    map: map,
    draggable: true,
    animation: google.maps.Animation.DROP,
    position: {
      lat: parseFloat('30.365273'),
      lng: parseFloat('-81.699600')
    }
  });
  marker.addListener('click', toggleBounce);
}
google.maps.event.addDomListener(window, "load", initMap);

html,
body,
#map {
  height: 100%;
  width: 100%;
  margin: 0px;
  padding: 0px
}

<script src="https://maps.googleapis.com/maps/api/js"></script>
<div id="map"></div>

change your PHP to be:

function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 13,
    center: {lat: parseFloat('<?php echo $lat;?>'), lng: parseFloat('<?php echo $lng;?>')}
  });

  marker = new google.maps.Marker({
    map: map,
    draggable: true,
    animation: google.maps.Animation.DROP,
    position: {lat: parseFloat('<?php echo $lat;?>'), lng: parseFloat('<?php echo $lng;?>')}
  });
  marker.addListener('click', toggleBounce);
}

</div>

I think having the PHP echo the value directly into your JavaScript is likely the problem. Try passing lat and lng as parameters to your map function instead.

function initMap(myLat, myLng) {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 13,
    center: new google.maps.LatLng(myLat, myLong)
  });

  marker = new google.maps.Marker({
    map: map,
    draggable: true,
    animation: google.maps.Animation.DROP,
    position: new google.maps.LatLng(myLat, myLong)
  });
  marker.addListener('click', toggleBounce);
}

Edit: try using the Google Maps function for setting latitude and longitude, as above.