php - 在php中没有重复的有序组合？

Question

我有以下数组：

数组（“一”、“二”、“三”、“四”）；

我需要一个函数来输出数组元素的所有有序组合而不重复。输出应该是

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

输出不应包括：

one one
one two four
two one three
four two three

等等 ...

你们中有人已经实施过这种算法吗？

Answer 1

这只是两个嵌套循环：

在线演示

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"));