For the number of calendar days between two dates (not the number of 24 hour amounts):

$fecha = "13-10-2016 00:00:00";
$dt_epoch_days= floor(date('U',strtotime($fecha))/(60*60*24)); 
$now_epoch_days= floor(date('U')/(60*60*24)); 
echo $now_epoch_days-$dt_epoch_days;