PHP は 2 つの日付の差を年、月、日で計算します。

<?php 
    
/** 
  +---------------------------------------------------------- 
 * 功能：计算两个日期相差 年 月 日 
  +---------------------------------------------------------- 
 * @param  date     $date1 起始日期 
 * @param  date     $date2 截止日期日期 
  +---------------------------------------------------------- 
 * @return array              
  +---------------------------------------------------------- 
 */
function DiffDate($date1, $date2) { 
    if (strtotime($date1) > strtotime($date2)) { 
        $ymd = $date2; 
        $date2 = $date1; 
        $date1 = $ymd; 
    } 
    list($y1, $m1, $d1) = explode('-', $date1); 
    list($y2, $m2, $d2) = explode('-', $date2); 
    $y = $m = $d = $_m = 0; 
    $math = ($y2 - $y1) * 12 + $m2 - $m1; 
    $y = round($math / 12); 
    $m = intval($math % 12); 
    $d = (mktime(0, 0, 0, $m2, $d2, $y2) - mktime(0, 0, 0, $m2, $d1, $y2)) / 86400; 
    if ($d < 0) { 
        $m -= 1; 
        $d += date('j', mktime(0, 0, 0, $m2, 0, $y2)); 
    } 
    $m < 0 && $y -= 1; 
    return array($y, $m, $d); 
} 
?>