$date = mysql_real_escape_string($_POST['intake_date']);

$date = mysql_real_escape_string($_POST['intake_date']);

$date = date('Y-m-d', strtotime(str_replace('-', '/', $date)));

$date = date('Y-m-d H:i:s', strtotime(str_replace('-', '/', $date)));

$date = '02/07/2009 00:07:00';
$date = preg_replace('#(d{2})/(d{2})/(d{4})s(.*)#', '$3-$2-$1 $4', $date);
echo $date;

2009-07-02 00:07:00

$mysqldate = date( 'Y-m-d H:i:s', $phpdate );
$phpdate = strtotime( $mysqldate );

$query = "UPDATE table SET
    datetimefield = FROM_UNIXTIME($phpdate)
    WHERE...";
$query = "SELECT UNIX_TIMESTAMP(datetimefield)
    FROM table WHERE...";

mysql> SELECT UNIX_TIMESTAMP(NOW());
+-----------------------+
| UNIX_TIMESTAMP(NOW()) |
+-----------------------+
|            1311343579 |
+-----------------------+
1 row in set (0.00 sec)

mysql> SELECT FROM_UNIXTIME(1311343579);
+---------------------------+
| FROM_UNIXTIME(1311343579) |
+---------------------------+
| 2011-07-22 15:06:19       |
+---------------------------+
1 row in set (0.00 sec)

$mysqlDate = date('Y-m-d H:i:s', strtotime($_POST['intake_date']));

$date = explode('/', $_POST['posted_date']);
$new_date = $date[2].'-'.$date[1].'-'.$date[0];

$new_date = $date[2].'-'.$date[0].'-'.$date[1];

function my_date_parse($date)
{
        if (!preg_match('/^(d+).(d+).(d+)$/', $date, $m))
                return false;

        $day = $m[1];
        $month = $m[2];
        $year = $m[3];

        if (!checkdate($month, $day, $year))
                return false;

        return "$year-$month-$day";
}

$date = explode($_POST['intake_date'], '/');
    mysql_date = $date[2].'-'$date[1].'-'$date[0];

$mysql_date = "2012-01-02";   // date in Y-m-d format as MySQL stores it
$date_obj = date_create_from_format('Y-m-d',$mysql_date);
$date = date_format($date_obj, 'm/d/Y');
echo $date;

01/02/2012

$php_date = "01/02/2012";
$update_query = "UPDATE `appointments` SET `start_time` = STR_TO_DATE('" . $php_date . "', '%m/%d/%Y')";
$query = "SELECT DATE_FORMAT(`start_time`,'%m/%d/%Y') AS `start_time` FROM `appointments`";