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<?php $days = array('Monday' => array('open_at' => '09:00', 'close_at' => '18:00'), 'Tuesday' => array('open_at' => '11:00', 'close_at' => '14:00') ); foreach ($days as &$day) { $time = new DateTime($day['open_at']); $close = new DateTime($day['close_at']); while ($time < $close) { $day[] = $time->format('H:i'); $time->modify('+15 minutes'); } } print_r($days);

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