Add date to MySQL using PHP -

i trying add current date mysql table using php. have following code:

$date = date('y-m-d'); mysql_query("insert book_order values($date)")  or die (mysql_error());

mysql returns error:

incorrect date value: '1996' column 'date_order' @ row 1

date_order attribute type date.

i've tried echo $date value , prints out 2013-05-12

why can't add date table , strange 1996?

if can send local date use:

mysql_query("insert book_order values(now())");

the problem because sql have typo - $date variable must quoted:

mysql_query("insert book_order values('$date')")  or die (mysql_error());

in addition, if not work edit question , paste result sql explain book_order

DIs