Laravel 8 Arr::crossJoin() {#collection-method}

Arr::crossJoin 函数交叉连接给定的数组，返回具有所有可能排列的笛卡尔乘积：

use Illuminate\Support\Arr;

$matrix = Arr::crossJoin([1, 2], ['a', 'b']);

/*
    [
        [1, 'a'],
        [1, 'b'],
        [2, 'a'],
        [2, 'b'],
    ]
*/

$matrix = Arr::crossJoin([1, 2], ['a', 'b'], ['I', 'II']);

/*
    [
        [1, 'a', 'I'],
        [1, 'a', 'II'],
        [1, 'b', 'I'],
        [1, 'b', 'II'],
        [2, 'a', 'I'],
        [2, 'a', 'II'],
        [2, 'b', 'I'],
        [2, 'b', 'II'],
    ]
*/