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<?php $yearMonth = '2017-06'; $firstDayOfThisMonth = new \DateTime($yearMonth . '-01'); var_dump($firstDayOfThisMonth->format('W')); $lastDayOfThisMonth = clone $firstDayOfThisMonth; $lastDayOfThisMonth = $lastDayOfThisMonth->modify('last day of this month'); var_dump($lastDayOfThisMonth->format('W'));

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