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<?php $arr = ['aaa', 'bbb', 'ccc', 'ddd']; $k = count($arr); $query = []; $parents = []; for ($i = 1; $i < $k; $i++) { for ($j = 0; $j < $k; $j++) { if ($j < $k - $i) { $query[$i][] = $arr[$j]; $parents[2 * $k - 1 - $j][] = $arr[$j]; } else { $query[2 * $k - 1 - $j][] = $arr[$j]; $parents[$i][] = $arr[$j]; } } } var_dump($query, $parents);
Output for 7.0.0 - 7.0.31, 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 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
array(6) { [1]=> array(3) { [0]=> string(3) "aaa" [1]=> string(3) "bbb" [2]=> string(3) "ccc" } [4]=> array(3) { [0]=> string(3) "ddd" [1]=> string(3) "ddd" [2]=> string(3) "ddd" } [2]=> array(2) { [0]=> string(3) "aaa" [1]=> string(3) "bbb" } [5]=> array(2) { [0]=> string(3) "ccc" [1]=> string(3) "ccc" } [3]=> array(1) { [0]=> string(3) "aaa" } [6]=> array(1) { [0]=> string(3) "bbb" } } array(6) { [7]=> array(3) { [0]=> string(3) "aaa" [1]=> string(3) "aaa" [2]=> string(3) "aaa" } [6]=> array(2) { [0]=> string(3) "bbb" [1]=> string(3) "bbb" } [5]=> array(1) { [0]=> string(3) "ccc" } [1]=> array(1) { [0]=> string(3) "ddd" } [2]=> array(2) { [0]=> string(3) "ccc" [1]=> string(3) "ddd" } [3]=> array(3) { [0]=> string(3) "bbb" [1]=> string(3) "ccc" [2]=> string(3) "ddd" } }

preferences:
109.74 ms | 2093 KiB | 4 Q