Hello,
No trick to it. To get array_push() to psuh items onto a multi-dimensional stack, just name that particular place within the stack as the place to do the pushing.
So to push a new plate on the stack within the array do something like:
array($groups[0][version], $version);
If you needed to push a new entire group on, you would create the groups array first, then push the group onto the stack.
$group = Array("anime5", 3, 7);
array_push($groups, $group);
This would push the whole thing, multiple dimensions and all, onto your main stack.