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<?php $time = 1456034400; $firstDay = strtotime('first Sunday of '.date('M',$time).' '.date('Y', $time)); $lastDay = mktime(0,0,0,date('m',$time)+1,1,date('Y', $time)); $weekdays = array(); for ($i = $firstDay; $i < $lastDay; $i += 7*24*3600){ $weekdays[] = date('d',$i); } var_dump($weekdays);
Output for 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.25, 8.4.1 - 8.4.12
array(4) { [0]=> string(2) "07" [1]=> string(2) "14" [2]=> string(2) "21" [3]=> string(2) "28" }

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