php计算到指定日期还有多少天的方法，php日期

function countdays($d) { $olddate = substr($d, 4); $newdate = date(Y) ."".$olddate; $nextyear = date(Y)+1 ."".$olddate; if($newdate > date("Y-m-d")) { $start_ts = strtotime($newdate); $end_ts = strtotime(date("Y-m-d")); $diff = $end_ts - $start_ts; $n = round($diff / 86400); $return = substr($n, 1); return $return; } else { $start_ts = strtotime($nextyear); $end_ts = strtotime(date("Y-m-d")); $diff = $end_ts - $start_ts; $n = round($diff / 86400); $return = substr($n, 1); return $return; } }