Probability string grouping:

I am studying about Machine learning and how to use with chatbots, however I came across a problem:

How to group the possibilities of a numeric representation of a string, eg:

1 1 5 1 2 1 

I'm trying to convert this to something like:

11 5  1  2  1
1  15 1  2  1
1  1  51  2 1
1  1  5  12 1
1  1  5  1  21
11 51 2  1
11 51 21
11 5  12 1

That is, test the possibilities, but without losing the order of the values (seria um fator linear ?) .

I have tried in many ways, but I believe it is not in the correct logic, all the functions that I tried to create or found ready, follow the pattern of this:

function pc_permute($items, $perms = array( )) {
    if (empty($items)) { 
        print join(' ', $perms) . "\n";
    }  else {
        for ($i = count($items) - 1; $i >= 0; --$i) {
             $newitems = $items;
             $newperms = $perms;
             list($foo) = array_splice($newitems, $i, 1);
             array_unshift($newperms, $foo);
             pc_permute($newitems, $newperms);
         }
    }
}
print_r(pc_permute($ns));

Permutations - all possible sets of numbers

I have achieved the same result in several different ways, that is, I have achieved all possibilities, even if they shuffle the numbers, in my case I can not take advantage of it.

  

How could I find the possibilities of grouping an array without losing the natural order of the same array?

OBS:

The answer can be in a mathematical representation, then I could solve the problem.