I am trying to output a JSON string using PHP and MySQL but the latitude and longitude is outputting as a string with quotes around the values. This causes an issue when I am trying to add the markers to a google map. 

Here is my code:

```
$sql = mysql_query('SELECT * FROM markers WHERE address !=""');
$results = array();
while($row = mysql_fetch_array($sql))
{
   $results[] = array(
      'latitude' =>$row['lat'],
      'longitude' => $row['lng'],
      'address' => $row['address'],
      'project_ID' => $row['project_ID'],
      'marker_id' => $row['marker_id']
   );
}
$json = json_encode($results);

echo "{\"markers\":";
echo $json;
echo "}";

```

Here is the expected output:

```
{"markers":[{"latitude":0.000000,"longitude":0.000000,"address":"2234 2nd Ave, Seattle, WA","project_ID":"7","marker_id":"21"}]}

```

Here is the output that I am getting:

```
{"markers":[{"latitude":"0.000000","longitude":"0.000000","address":"2234 2nd Ave, Seattle, WA","project_ID":"7","marker_id":"21"}]}

```

Notice the quotes around the latitude and longitude values.