Php 如何从一年中的某一天转到日期，反之亦然

这很容易。您应该在此处阅读对象的静态方法，在此处阅读函数，在此处阅读函数。DateTimecreateFromFormatdatestrtotime

// This should get you a DateTime object from the date and year.
function getDateFromDay($year, $dayOfYear) {
  $date = DateTime::createFromFormat('z Y', strval($year) . ' ' . strval($dayOfYear));
  return $date;
}

// This should get you the day of the year and the year in a string.
date('z Y', strtotime('21 oct 2012'));

尝试（天数从非开始）：01

$date = DateTime::createFromFormat( 'Y z' , '2012 275');
var_dump($date);

并且：

echo date('z', strtotime('21 oct 2012'));