having trouble updating multiple records with implode

I am trying to update multiple records based on an array that is posted.

It works if the array has only 1 item but two or more and it fails to work.

if (isset($_POST['checkboxArray'])) {
    if (isset($_POST['archiveit'])){
        $checkbox = $_POST['checkboxArray'];
        $mID = implode( ",", $checkbox );
        $sql ="update simpleNote SET status='archived' WHERE  mID = '$mID'";

        if ($conn->query($sql) === TRUE) {
            echo "Items moved to archived.";
        } else {
            echo "Error archiving Messages: " . $conn->error . "<br/> SQL: " . $sql;
        }

        $conn->close();
    }
    if (isset($_POST['trashit'])){
        $checkbox = $_POST['checkboxArray'];
        $mID = implode( ",", $checkbox );
        $sql ="update simpleNote SET status='deleted' WHERE  mID = '$mID'";

        if ($conn->query($sql) === TRUE) {
            echo "Items deleted.";
        } else {
            echo "Error deleting Messages: " . $conn->error . "<br/> SQL: " . $sql;
        }

        $conn->close();
    }
}

Select all Open in new window