Discussion: How to use PHP to calculate the number of years months weeks and days between two dates

PHP is used to calculate the number of years, months, weeks and days between two dates:

<?php
    function format($a,$b){
        // Check the two date sizes, default small before and large after, and switch positions if large before and small after to ensure large before and large after 
        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){                // If less than 7 Days returns days directly 
            $result['daily'] = $extend;
        }elseif($extend<=31){        // Less than 28 Days return the number of weeks due to leap years 2 Month to satisfy the 
            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){                // If more than 1 years 
                $start = strtotime($a.'+'.$y.'year');
                $a     = date('Y-m-d',$start);
                // Determine if it's already there 1 Years. If not, subtract 
                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'));
?>

Operation results:
Array([extends]= > 75[monthly]= > 2[weekly]= > 2)

php queries the week of a day and the start date of the corresponding week

/**
* @file
* @version  1.1
* @author  QQ83989686
* @date  2012-8-7  Last modified time 
* @brief 
*/
    // Gets a date   Weeks, weeks corresponding to the start and end time 
    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)-($g-1)*86400),'week_start_day_cn'=>strftime('%Y years %m month %d day ',strtotime($day)-($g-1)*86400),'week_end_day'=>strftime('%Y-%m-%d',strtotime($day) + (7-$g)*86400),'week_end_day_cn'=>strftime('%Y years %m month %d day ',strtotime($day) + (7-$g)*86400));
    }