探讨:如何使用PHP实现计算两个日期间隔的年、月、周、日数

function format($a,$b){
//检查两个日期大小，默认前小后大，如果前大后小则交换位置以保证前小后大
if(strtotime($a)>strtotime($b)) list($a,$b)=array($b,$a);
$start = strtotime($a);
$stop = strtotime($b);
$extend = ($stop-$start)/86400;
$result['extends'] = $extend;
if($extend<7){ //如果小于7天直接返回天数
$result['daily'] = $extend;
}elseif($extend<=31){ //小于28天则返回周数，由于闰年2月满足了
if($stop==strtotime($a.'+1 month')){
$result['monthly'] = 1;
}else{
$w = floor($extend/7);
$d = ($stop-strtotime($a.'+'.$w.' week'))/86400;
$result['weekly'] = $w;
$result['daily'] = $d;
}
}else{
$y= floor($extend/365);
if($y>=1){ //如果超过一年
$start = strtotime($a.'+'.$y.'year');
$a = date('Y-m-d',$start);
//判断是否真的已经有了一年了，如果没有的话就开减
if($start>$stop){
$a = date('Y-m-d',strtotime($a.'-1 month'));
$m =11;
$y--;
}
$extend = ($stop-strtotime($a))/86400;
}
if(isset($m)){
$w = floor($extend/7);
$d = $extend-$w*7;
}else{
$m = isset($m)?$m:round($extend/30);
$stop>=strtotime($a.'+'.$m.'month')?$m:$m--;
if($stop>=strtotime($a.'+'.$m.'month')){
$d=$w=($stop-strtotime($a.'+'.$m.'month'))/86400;
$w = floor($w/7);
$d = $d-$w*7;
}
}
$result['yearly'] = $y;
$result['monthly'] = $m;
$result['weekly'] = $w;
$result['daily'] = isset($d)?$d:null;
}
return array_filter($result);
} print_r(format('2012-10-1','2012-12-15'));
?>

/**
* @file
* @version 1.1
* @author QQ83989686
* @date 2012-8-7 最后修改时间
* @brief
*/
//获取某个日期的 周数、周对应的开始结束时间
private function getWeekStartEndDay($day)
{
$g = strftime("%u",strtotime($day));
return array('week_num'=>strftime("%V",strtotime($day)),'week_start_day'=>strftime('%Y-%m-%d',strtotime($day)-($g-1)*86400),'week_start_day_cn'=>strftime('%Y年%m月%d日','week_end_day'=>strftime('%Y-%m-%d',strtotime($day) + (7-$g)*86400),'week_end_day_cn'=>strftime('%Y年%m月%d日',strtotime($day) + (7-$g)*86400));
}