PowerShell Snippet to Check Whether WebApplication Level Feature is Activated or not if not then Activate the Feature

<#
.SYNOPSIS
Activating WebApplication level features if not already activated

.PARAMETER Url
The URL of the web application

.PARAMETER featureID
ID of feature which need to be activated
#>

param
(
[parameter(Mandatory=$true)][string]$Url,
[parameter(Mandatory=$true)][string]$featureID
)

#Activate web application Feature
#----------------------------------------------------
$webApplication = Get-SPWebApplication -Identity $Url

#Check whether Feature to be activated is already activated
$feature = Get-SPFeature -WebApplication $webApplication | where {$_.Id -eq $fatureID}

if ($feature)
{
      Write-Host "feature with ID" $fatureID "is already activated"
}
else
{
      Enable-SPFeature -Identity $fatureID -Url $webApplication.url
      Write-Host "feature with ID" $fatureID "has been activated at :" $webApplication.url
}