Find the number of days between two dates using PHP

function maketime($date)
{
 list($year,$month,$day) = explode("-",$date);
 return mktime(0,0,0, $month,$day,$year);
}

$date1 = "2015-01-01";
$date2 = "2015-01-05";
$d = (maketime($date2) - maketime( $date1)) / (3600*24);
echo "$date1 - $date2 $d days apart";
?>

PHP