php json_encode 数据请求

如何解决php json_encode 数据请求

我从我的 sql 查询中获取数据，然后我尝试对这些数据进行 json_encode，但这返回一个 false

    $response = array();
    $request = $conn->query("SELECT * FROM mytest");
    while ($row = $request->fetch_array()){
        $response[] = $row;
    }
    var_dump($response);
    header('Content-Type: application/json');
    echo json_encode($response,JSON_PRETTY_PRINT);

我的回声是空的，原因是返回假，我的 var_dump($response) 返回我：

array (size=12)
  0 => 
    array (size=8)
      0 => string '1' (length=1)
      'id' => string '1' (length=1)
      1 => string 'b�lier' (length=6)
      'sign' => string 'b�lier' (length=6)
      2 => string 'description du b�lier' (length=21)
      'description' => string 'description du b�lier' (length=21)
      3 => string '2021-05-22' (length=10)
      'date' => string '2021-05-22' (length=10)
  1 => 
    array (size=8)
      0 => string '2' (length=1)
      'id' => string '2' (length=1)
      1 => string 'taureau' (length=7)
      'sign' => string 'taureau' (length=7)
      2 => string 'description du taureau' (length=21)
      'description' => string 'description du taureau' (length=21)
      3 => string '2021-05-22' (length=10)
      'date' => string '2021-05-22' (length=10)