PHP - 将数组值组合成两个唯一的对

Question

我正在尝试转换以下数组

    Array
    (
        [304] => Array
            (
                [0] => 102
                [1] => 177
                [2] => 132
                [3] => 223
            )
        [302] => Array
            (
                [0] => 132
                [1] => 96
            )
    )

进入以下内容：

    Array
    (
        [0] => Array
            (
                ["source"] => 102
                ["target"] => 177
            )
        [1] => Array
            (
                ["source"] => 102
                ["target"] => 132
            )
        [2] => Array
            (
                ["source"] => 102
                ["target"] => 223
            )
        [3] => Array
            (
                ["source"] => 177
                ["target"] => 132
            )
        [4] => Array
            (
                ["source"] => 177
                ["target"] => 223
            )
        [4] => Array
            (
                ["source"] => 132
                ["target"] => 223
            )
        // only two values, so just one pair
        [5] => Array
            (
                ["source"] => 132
                ["target"] => 96
            )
    )

这样我就得到了所有可能的对，没有任何重复！

我尝试了很多东西，比如使用 if 语句的循环中的循环，但我不知道从哪里开始......
一个例子是：

    $new_links = array();
     foreach($arr as $arr_new){
      foreach($arr_new as $key => $value){
        if($key == 0){
          $source=$value;
        }else{
          $new_links[$key]["source"]=$source;
          $new_links[$key]["target"]=$value;
        }
      }
     }

其中 $arr 是给定的数组

所以我的问题是：实现这一目标的最有效方法是什么？

提前致谢！！

- - - 编辑 - - -

感谢chba ！！

我只需要稍微编辑一下语法就可以让它运行，但逻辑就像一个魅力！！

我的最终结果是：

    // the given array is $arr
    $result = array();

    foreach ($arr as $group)
    {
        $lastIdx = count($group) - 1;
        $startIdx = 1;

        foreach ($group as $member)
        {
            for ($pos = $startIdx; $pos <= $lastIdx; $pos++)
            {
                $result[] = array(
                    'source' => $member,
                    'target' => $group[$pos]
                );
            }

            $startIdx++;
        }
    }

Answer 1

<?php

$input = [[102,177,132,223],[132,96]];
$result = [];

// for each group of elements in input array
foreach ($input as $group)
{
    // set the first target element of the group to be
    // second element
    $nextTargetIdx = 1;

    // determine last target index beforehand
    // so that value gets computed only once per group
    $lastTargetIdx = count($group) - 1;

    // then, take each element of that group as source
    foreach ($group as $source)
    {
        // and 
        for // every next element
        (
            $targetIdx = $nextTargetIdx;
            $targetIdx <= $lastTargetIdx;
            $targetIdx++
        )
        {
            // add new result entry
            $result[] = [
                // with current source
                'source' => $source,
                // and target
                'target' => $group[$targetIdx]
            ];
        }

        // then, when all targets for current source are found
        // increase next target index so that it follows next source element
        $nextTargetIdx++;
    }
}

var_dump($result);