randomized a awt of Arrays but some values were group together

Hi I have a set or array:

$arr = ['1','2','3','4','5','6','7','8','9','0'];
shuffle($arr);

this will return the randomized order of the array. but how can I code if the '3','4' and '8','9','0' must together? I mean the other value can go random order but these '3','4' and '8','9','0' must join together.