PowerShell function to add a path to the PATH environment variable

Add-EnvPath.ps1

<#
.Synopsis
Add a path to the PATH environment variable.
.Description
Adds the given path to the paths defined in the PATH environment variable.
The path is only added if it is not already in PATH and it actually resolves to an existing directory.
Empty paths (empty strings) are not added and any empty paths in PATH are removed. Add '.' to refer to the current directory.
.Parameter Path
The path to be added. It is being tested if it leads to an existing object. If not, it is not added.
.Parameter Prepend
Add the path to the beginning of paths listed in PATH. By default, paths are added at the end.
.Parameter Category
The PATH variable category to modify. An empty (default) category denotes env:PATH. A non-empty category denotes an environment PATH variable which name    starts with the given category. E.g. category MAN denotes env:MANPATH.
#>
function Add-EnvPath {
    param(
        [Parameter(Mandatory=$true)]
        [string] $Path,

        [Parameter(Mandatory=$false)]
        [Switch] $Prepend,

        [Parameter(Mandatory=$false)]
        [string] $Category
    )

    if (Test-Path -Path $Path) {
        if (Test-Path -Path Env:${Category}PATH) {
            $envPaths = (Get-Content -Path Env:${Category}PATH) -split [IO.Path]::PathSeparator
        } else {
            $envPaths = @()
        }
        if ($envPaths -notcontains $Path) {
            if ($Prepend) {
                $envPaths = ,$Path + $envPaths | where { $_ }
            } else {
                $envPaths = $envPaths + $Path | where { $_ }
            }
            Set-Content -Path Env:${Category}PATH -Value ($envPaths -join [IO.Path]::PathSeparator)
        }
    }
}