PowerShell : List All the users for a Site Collection

if ((Get-PSSnapin "Microsoft.SharePoint.PowerShell" -ErrorAction SilentlyContinue) -eq $null) {
    Add-PSSnapin "Microsoft.SharePoint.PowerShell"
}
param
(
    [parameter(Mandatory=$false)][string]$RootSiteUrl = "<Your Site Collection URL goes here>"
)


# Array to hold the user collection
$userCollection = @()

$users = Get-SPUser -Web $RootSiteUrl -Limit ALL
foreach ($domainUser in $users)
{
    # Get Domain from user login name
    $domainUserSTR = $domainUser.Userlogin
    $domain = $domainUserSTR.Split("\")[0]
    $ispipe = $domain.IndexOf("|")
    if ($ispipe -ne -1)
    {
        $domain = $domain.split("|")[1]
    }

    $user = New-Object System.Object
    $user | Add-Member -MemberType NoteProperty -Name "Domain" -Value $domain
        $user | Add-Member -MemberType NoteProperty -Name "UserLogin" -Value $domainUser.UserLogin
    $user | Add-Member -MemberType NoteProperty -Name "DisplayName" -Value $domainUser.DisplayName

    $userCollection  += $user

    Write-Host $user.UserLogin
}

$userCollection | Export-CSV -Path "C:\UserLists.csv" -NoTypeInformation
Write-Host "Finished."