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<?php function permutation($arr) { while($ele=array_shift($arr)) { $row=array($ele); foreach($arr as $rest) { $row[]=$rest; if(count($row)==2) var_dump($row); } } } permutation(array("1","2","3","4"));
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.24 - 5.5.35, 5.6.7 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.0 - 7.2.33, 7.3.12 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
array(2) { [0]=> string(1) "1" [1]=> string(1) "2" } array(2) { [0]=> string(1) "2" [1]=> string(1) "3" } array(2) { [0]=> string(1) "3" [1]=> string(1) "4" }

preferences:
202.11 ms | 406 KiB | 314 Q