theres a few ways to do this:
1) Set the default value for the date column to:
CURRENT_TIMESTAMP
Then no binding is needed in the insert, the database will automatically set the date column to the current date on insert.
2) create a hidden element and set the value to:
<?php echo(date("Y-m-d h:i:s")); ?>
the bind the date column to the hidden element
3) Instead of binding to the hidden element, set the code for the date column to:
<?php echo(date("Y-m-d h:i:s")); ?>