print_membergroup_row() and array() Help !

[K a M a L]

sorry , it is my second thread today
I'm programming admin page and used the function

PHP Code:

print_membergroup_row (string $title, [string $name = 'membergroup'], [integer $columns = 0], [mixed $userarray = NULL]) 


My strange problem is with last arrtibute , it is used to prefill usergrups with current values
when I write

PHP Code:

    print_membergroup_row("Title", "recusergroup",2,array('usergroupid' => 0, 'membergroupids' => '1,2,3,4,5,6')); 


it works correctly and groups 1,2,3,4,5,6 are marked
I have variabe

PHP Code:

$groups=1,2,3,4,5,6 


when I write

PHP Code:

print_membergroup_row("Title", "recusergroup",2,array('usergroupid' => 0, 'membergroupids' => $groups)); 


I get only group 1 marked
then I set

PHP Code:

$groups='1,2,3,4,5,6' 


it doesn't work correctly
the first and last number are ignored !! and groups 2,3,4,5 only marked !