PHP通过逗号从mysql中提取geojson

下面是我的php和geojson的样子。我想用逗号将它们分开,除了最后一个“while query”,因为它与传单一起工作。我试着在$data['geojson']后面回显一个逗号,但它在结尾也回显一个逗号,这使它无法工作。现在只要数据库中只有一行,它就可以工作。

geojson存储在geojson列中,每个geojson行都有自己的行

    $sql = "SELECT * FROM `polygons` ORDER BY id";

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

    $check = mysqli_num_rows($result);
    if($check > 0){
        echo '{"type":"FeatureCollection","features":[';
        
    while($data= mysqli_fetch_assoc($result)){
    
    echo $data["geojson"];
    
    
    }
    echo "]}";

GEOJSON:

{"type":"FeatureCollection","features":[{"type":"Feature","properties":{},"geometry":{"type":"Polygon","coordinates":[[[9.836037,54.92779],[9.79818,54.93067],[9.769213,54.924124],[9.745858,54.906048],[9.796566,54.879997],[9.860286,54.89273],[9.837761,54.925973],[9.836037,54.92779]]]}}


{"type":"Feature","properties":{},"geometry":{"type":"Polygon","coordinates":[[[9.855609,54.956418],[9.867858,54.923851],[9.971178,54.943613],[9.92426,54.969291],[9.855609,54.956418]]]}}]}