function getSundays($y, $m) {
return new DatePeriod(
new DateTime("first sunday of $y-$m"),
DateInterval::createFromDateString('next sunday'),
new DateTime("last day of $y-$m")
);
}
// Usage:
foreach (getSundays(2021, 03) as $sundays) {
echo $sundays->format("l, Y-m-d
");
}