将日期分组为一年中的星期，PHP

$dayOfWeek = date("l", strtotime("2022-01-01"));
echo $dayOfWeek; // 输出：Saturday

$weekNumber = date("W", strtotime("2022-01-01"));
echo $weekNumber; // 输出：01

function groupByWeek($dates) {
    $result = array();
    
    foreach ($dates as $date) {
        $weekNumber = date("W", strtotime($date));
        
        if (!isset($result[$weekNumber])) {
            $result[$weekNumber] = array();
        }
        
        $result[$weekNumber][] = $date;
    }
    
    return $result;
}

$dates = array("2022-01-01", "2022-01-02", "2022-01-03", "2022-01-08", "2022-01-09", "2022-01-10");
$groups = groupByWeek($dates);

foreach ($groups as $weekNumber => $dates) {
    echo "Week " . $weekNumber . ": " . implode(", ", $dates) . "\n";
}

// 输出：
// Week 01: 2022-01-01, 2022-01-02, 2022-01-03
// Week 02: 2022-01-08, 2022-01-09, 2022-01-10