How to display the GeoJSON from PHP on the map?

I am using MapboxGLJS. I retrieve the coordinates from my database and I put it in GeoJSON format on PHP which look like this:

   <?php 
            $sql = "SELECT * FROM waypoint";

            $server = "localhost";
            $username = "root";
            $password = "";
            $db = "scandrone";  
            $conn = mysqli_connect($server, $username, $password, $db);

            $result = mysqli_query($conn, $sql);

            $geojson = array('type' => 'FeatureCollection', 'features' => array());

                    while($row = mysqli_fetch_assoc($result)){
    $marker = array(    
            'type' => 'Feature',
            'features' => array(
                'type' => 'Feature',
                "geometry" => array(
                    'type' => 'Polygon',
                    'coordinates' => array(
                         $row['longitude'],
                         $row['latitude']

                    )
                )
            )
        );
    }

        echo json_encode($marker); 
?>

And when i did an “echo json_encode($marker);” i got this

[{"type":"geojson","data":{"type":"Feature","geometry":{"type":"Polygon","coordinates":{"longitude":"2.0556640625005","latitude":"45.641158147526"}}}},{"type":"geojson","data":{"type":"Feature","geometry":{"type":"Polygon","coordinates":{"longitude":"3.3959960937499","latitude":"44.852208244354"}}}},{"type":"geojson","data":{"type":"Feature","geometry":{"type":"Polygon","coordinates":{"longitude":"1.4404296875004","latitude":"44.508493826826"}}}}]

Now I need to display this on my map. How can I do this?

<?php 
$sql = "SELECT * FROM waypoint";

$server = "localhost";
$username = "root";
$password = "";
$db = "scandrone";  
$conn = mysqli_connect($server, $username, $password, $db);

$result = mysqli_query($conn, $sql);

$geojson = array('type' => 'FeatureCollection', 'features' => array());

while($row = mysqli_fetch_assoc($result)) {
    $marker = array(
        'type' => 'Feature',
        'features' => array(
            'type' => 'Feature',
            "geometry" => array(
                'type' => 'Polygon',
                'coordinates' => array(
                     $row['longitude'],
                     $row['latitude']
                )
            )
        )
    );
    array_push($geojson['features'], $marker);
}

echo json_encode($geojson); 
?>