el formato debe ser anio/mes/dia
Código PHP:
$date = '17/07/2010 22:45';
$format = '%d/%m/%Y %H:%M';
$a = strptime($date, $format);
$timestamp = mktime($a['tm_hour'], $a['tm_min'], 0, $a['tm_mon'], $a['tm_mday'], $a['tm_year'] + 1900);
echo $timestamp;
echo '<br>';
echo '<br>'. date('Y/m/d H:i',$timestamp);