<?php $b = [[1,2],[2,3],[3,4]]; ?>
Standard input is empty
Array
(
[-1] =>
[0] => Array
(
[0] => 2
[1] => 1
)
[1] => Array
(
[0] => 3
[1] => 2
)
[2] => Array
(
[0] => 4
[1] => 3
)
)
Array
(
[0] => Array
(
[0] => 2
[1] => 3
[2] => 4
)
[1] => Array
(
[0] => 1
[1] => 2
[2] => 3
)
)