PHP排序多维数组 - array_multisort给出错误

I need to sort a dataset in php, It has this kind of structure:

$arr['col1'][0] = '12a';
$arr['col2'][0] = '6';
$arr['col1'][1] = '05m';
$arr['col2'][1] = '7l';

and I want to do something like this SQL:

select *
from $arr
order by col1, col2

I tryed this, but does not work

$col_1 = array_column($arr, 'col1');
$col_2 = array_column($arr, 'col2');
array_multisort($col_2, $col_1, $arr);

it gives "array sizes inconsistent"

desired order is:

05m  7l
12a  6