PHP: formatação de data e hora de SQL fácil

SQL para humano:

/* 
 * date
 */
$format = 'm/d/Y'; // en-US
// $format = 'd/m/Y'; // pt-BR
$date = '2012-02-01';
echo date($format, strtotime($date));


/* 
 * datetime
 */
$format .= ' H:i:s';
$datetime = '2012-02-01 11:33:59';
echo date($format, strtotime($datetime));

Humano para SQL:

/* 
 * date
 */
$sqlFormat = 'Y-m-d';
$date = '02/01/2012';

// en-US
echo date($sqlFormat, strtotime($date));
// pt-BR
echo join('-', array_reverse(explode('/', $date)));


/* 
 * datetime
 */
$sqlFormat = 'Y-m-d H:i:s';

// en-US
$datetime = '02/01/2012 11:33:59';  
echo date($sqlFormat, strtotime($datetime));

// pt-BR
$datetime = '01/02/2012 11:33:59';
$datetime = explode(' ', $datetime);
$date = join('-', array_reverse(explode('/', $datetime[0])));
echo $date . ' ' . $datetime[1];

http://rogeriolino.com/2012/02/01/php-easy-sql-date-time-formatting/