php数组，日期按周分组，从星期六到星期五

// 假设有一个包含日期的数组
$dates = array('2022-01-01', '2022-01-02', '2022-01-03', '2022-01-04', '2022-01-05', '2022-01-06', '2022-01-07', '2022-01-08', '2022-01-09', '2022-01-10', '2022-01-11', '2022-01-12', '2022-01-13', '2022-01-14', '2022-01-15', '2022-01-16', '2022-01-17', '2022-01-18', '2022-01-19', '2022-01-20', '2022-01-21', '2022-01-22', '2022-01-23', '2022-01-24', '2022-01-25', '2022-01-26', '2022-01-27', '2022-01-28', '2022-01-29', '2022-01-30', '2022-01-31');

// 将日期按周分组
$groups = array();
foreach ($dates as $date) {
    $weekNumber = date('W', strtotime($date));
    $groups[$weekNumber][] = $date;
}

// 输出分组结果
foreach ($groups as $weekNumber => $weekDates) {
    echo "第 " . $weekNumber . " 周:\n";
    foreach ($weekDates as $date) {
        echo $date . "\n";
    }
    echo "\n";
}