尝试下载Blob时获取null值

I have a problem to download images stored in my Mysql database as a Blob. I tried already a lot of solutions which I found in other post's but the result is every time the same, an echo "[{"image":null},{"image":null},{"image":null}]" I slim my code more and more to get the spot as small as possible but nothing. This is my last try which is actually a copy of this post :Empty PHP output from MySQL database for a longblob


    <?php
 
// Create connection
$con=mysqli_connect("Server","User","Pw","DBName");
 
// Check connection
if (mysqli_connect_errno())
{
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
    
// This SQL statement selects ALL from the table 'Locations'
$sql = "SELECT CAST(engineerSignature as CHAR(1000000) CHARACTER SET utf8) as engineerSignature FROM tblservreport";
    
if ($result = mysqli_query($con, $sql)){
    
    $resultArray = array();
    $tempArray = array();
 
    // Loop through each row in the result set
    while($row = $result->fetch_object())
    {       
            $tempArray = $row;
            array_push($resultArray, $tempArray);

    }
    
    // Finally, encode the array to JSON and output the results
    echo json_encode($resultArray);
}

mysqli_close($con);
?>

但它也不起作用。 我看错地方了吗? 我确定图片可以正常运行,因为我在Win.PC上有另一个程序,并且我直接下载了该程序,而没有通过PHP的方式,并且可以正常运行。 请我阅读很多答案,因为这不是将图像存储在这样的数据库中的好方法,但这不是我必须遵循的这种选择。 我希望有人也能看到我想念的东西或对我可以尝试的东西有所了解?