<?php $sql = "SELECT estimated_sum FROM burndown_snap WHERE project_id='$sum1 AND name='$sum2'";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
while($row = $result->fetch_assoc()) {
    $burn_actual = "" . $row["estimated_sum"]. ",";
    echo $burn_actual;
}
}
?>

<?php $sql = "SELECT estimated_sum FROM burndown_snap WHERE project_id='$sum1 AND name='$sum2'";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
while($row = $result->fetch_assoc()) {
    $burn_actual = "" . $row["estimated_sum"]. ",";
    echo $burn_actual;
}
}
?>

<?php echo $burn_actual; ?>