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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 - 7.2.0
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" }