php mysql grabbing date time automatically?

[piki to to loss]

Hi,
you know how with tables in databases you can set an id field to auto increment so tht when u insert values u can just leave tht field blank and it will auto increment from the last time?

likewise is it possible for me to set type so that if i leave the field blank (when inserting values) it will automatically grab the date and time? If so how could i do this?

Also if this isn't possible how can I use php to grab the date and time from the users computer?

Thanks for any input!