Save current timestamp in MySQL using PHP mysqi binding

If you have a filed defined and timestamp in MySQL table and you want to insert or update the field using mysqli binding, you can make use of the now() function of MySQL

$query = "INSERT INTO my_table VALUES ('text1',now())";
mysqli_query($mysqli, $query);

$query = "UPDATE my_table SET $topicId=?, $topicName=?, created_date=now()";
$stmt -> bind_param("ss",$topic_name,$topic_desc);
$stmt -> execute();
$stmt -> close();