在php中沒有重複的順序組合？

Question

我有以下數組：

Array（「one」，「two」，「three」，「four」）;

我需要一個函數來輸出數組元素的所有有序組合，而不需要重複。輸出應該

one 
one two 
one two three 
one two three four 
two 
two three 
two three four 
three 
three four 
four 

輸出不應該包括：

one one 
one two four 
two one three 
four two three 

等等......

難道你們有人已經實施這種alghoritm的？

Answer 1

這僅僅是兩個嵌套的循環：

Online demo

function permutation(array $arr) 
{ 
    while($ele=array_shift($arr)) 
    { 
     $x=$ele; 
     echo $x."\n"; 
     foreach($arr as $rest) 
     { 
      $x.=" $rest"; 
      echo $x."\n"; 
     } 
    } 
} 
permutation(array("one","two","three","four"));