It’s a very useful code. Sometimes after activating features, installing solutions or anything else you need to make iisreset on all the application servers of your SharePoint farm.

#IISReset on all application servers in a farm 
if ((Get-PSSnapin "Microsoft.SharePoint.PowerShell" -ErrorAction SilentlyContinue) -eq $null) 
    Write-Host "Connect Sharepoint library" 
    Add-PSSnapin Microsoft.SharePoint.PowerShell 

$farm = Get-SPFarm 
$servers = Get-SPServer | Where { $_.Role -eq "Application"} 
foreach($server in $servers)  { 
     Write-Host -ForegroundColor Red “Attempting to iisreset on server $server” 
         iisreset $server /noforce 
         iisreset $server /status 
         Write-Host -ForegroundColor Green “iisreset has been successfully done on server $server”