php 二维数组排列组合

Question

 Array
(
    [0] => Array
        (
            [0] => m
            [1] => n
        )

    [1] => Array
        (
            [0] => a
            [1] => e
        )

    [2] => Array
        (
            [0] => he
            [1] => hu
            [2] => huo
        )

    [3] => Array
        (
            [0] => b
        )

)

希望的结果

 array(
    [0]    =>  m,a,he,b
    [1]    =>  m,e,he,b
    [2]    =>  m,a,hu,b
    [3]    =>  m,e,hu,b
    [4]    =>  m,a,huo,b
    [5]    =>  m,e,huo,b
    [6]    =>  n,a,he,b
    [7]    =>  n,e,he,b
    [8]    =>  n,a,hu,b
    [9]    =>  n,e,hu,b
    [10] => n,a,huo,b
    [11] => n,e,huo,b
)

m,a,he,b
....
....
这些值得顺序不能变

求解

Answer 1

为什么要这样的结果？