PowerShell Nested ForEach Loop to get AD Sub Groups

Question

I have been trialing a script to get the AD groups and the groups within the groups an AD user in. The script is not effecient as to find a group within a group within a group I have had to use multiple foreach loops. Is it possible to make this command more efficient/smaller rather than using the foreach loop?

function GetADSubGroups ($object)
{
    Get-ADPrincipalGroupMembership $object | ForEach {
        $_
        Get-ADPrincipalGroupMembership $_ | ForEach {
        $_
        Get-ADPrincipalGroupMembership $_ | ForEach {
        $_
        Get-ADPrincipalGroupMembership $_ 
       }
    }
}
} 

GetADSubGroups 'testuser' | select name

Answer 1

You can use a while loop to eliminate all the foreach loops. Also remove the Select cmdlet's and use dot notation instead. All of this should speed it up by around 25%.

$groups = Get-ADPrincipalGroupMembership 'testuser'
$allGroups =$null

While($groups){
    $allGroups += $groups.Name
    $groups = $groups.Name | Get-ADPrincipalGroupMembership   
}

$allGroups