改变PHP数组结构，一位数组变二维数组

Question

PHP数组
$arr = [1,2,3,4,5,6,7,8,9,...];
改成
$arr = [[1,2,3],[4,5,6],[7,8,9],...];
有什么办法吗？
数组元素个数不固定。

Answer 1

$a = [1, 2, 3, 4, 5, 6, 7, 8, 9];
print_r(array_chunk($a, 3));

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

    [1] => Array
        (
            [0] => 4
            [1] => 5
            [2] => 6
        )

    [2] => Array
        (
            [0] => 7
            [1] => 8
            [2] => 9
        )

)