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<?php $yourArr = [1,2,1,2,3,4,5]; $res = array_count_values($yourArr); $res = array_filter($res, function($item){ return $item == 1; }); print_r(array_keys($res));
Output for 7.1.25 - 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 - 8.3.26, 8.4.1 - 8.4.13
Array ( [0] => 3 [1] => 4 [2] => 5 )

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