php实现数组的笛卡尔积

数组的笛卡尔积在实际中还是挺有用处的，比如计算商品的规格时就经常用到，下面写一种实现方式，如下代码

$arr = array(
    array(2),
    array(6,7),
    array('a','b','c')
  );
function dikaer($arr){
  $arr1 = array();
  $result = array_shift($arr);
  while($arr2 = array_shift($arr)){
    $arr1 = $result;
    $result = array();
    foreach($arr1 as $v){
      foreach($arr2 as $v2){
        if(!is_array($v))$v = array($v);
        if(!is_array($v2))$v2 = array($v2);
        $result[] = array_merge_recursive($v,$v2);
      }
    }
  }
  return $result;
}

以上例子输出的结果如下：

Array
(
    [0] => Array
        (
            [0] => 2
            [1] => 6
            [2] => a
        )

    [1] => Array
        (
            [0] => 2
            [1] => 6
            [2] => b
        )

    [2] => Array
        (
            [0] => 2
            [1] => 6
            [2] => c
        )

    [3] => Array
        (
            [0] => 2
            [1] => 7
            [2] => a
        )

    [4] => Array
        (
            [0] => 2
            [1] => 7
            [2] => b
        )

    [5] => Array
        (
            [0] => 2
            [1] => 7
            [2] => c
        )

)

如果需要输出字符串形式的结果可以把代码改成这样

function dikaer($arr){
  $arr1 = array();
  $result = array_shift($arr);
  while($arr2 = array_shift($arr)){
    $arr1 = $result;
    $result = array();
    foreach($arr1 as $v){
      foreach($arr2 as $v2){
        $result[] = $v.','.$v2;
      }
    }
  }
  return $result;
}

输出结果如下所示：

Array
(
    [0] => 2,6,a
    [1] => 2,6,b
    [2] => 2,6,c
    [3] => 2,7,a
    [4] => 2,7,b
    [5] => 2,7,c
)