Compare dynamic arrays with Powershell and some SharePoint

Today was a day I got to work on a revision to a script that I thought was working but apparently was not tested as well as I thought, not uncommon with pretty much everything I have done thus far. :) This is pretty well commented. I am starting to make use of templates when working with scripts to keep them looking a bit easier to understand.

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## DESCRIPTION ## ------------------------------------------------ ## Script to loop through a set of Subsites and a ## SharePoint List of items and then either ## create a new item or update it in your SharePoint List. ## ## EXPLAINATION ## ------------------------------------------------ ## This example illustrates how to compare 2 dynamically ## created arrays, look for the difference between ## the two, then do something like update a SharePoint list, ## this could also apply to updating a text file ## or csv/excel file ## ## BEGIN ## ------------------------------------------------ ## Load up the snapin so Powershell can work with SharePoint ## if the snapin was already loaded don't alert the user Add-PSSnapin microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue ## Clear any errors CLS ## Set variables ## This variable will be the site where all the subsites ## are that I want to get an array of $parentSite = "http://sp2010/clients" $rollupSite = "http://sp2010" ## Define the name of the SharePoint List we want to work with $rollupListName = "Orders" ## Initialize and create empty arrays $listOfSites = @() $listOfItems = @()   function GetListOfSites {  ## Create a variable to hold the SharePoint site, invoke the connection  ## to the site we defined in the $parentSite variable  $web = Get-SPWeb $parentSite  ## Check to make sure that url exists  if($web -ne $true)  {   ## Loop through all the sub sites of the site url we got   foreach($webSite in $web.Webs)   {    ## We have to use @() around the items we are going    ## to add to the array. The += means we want to    ## keep adding items into our array named $listOfSites    $listOfSites += @($webSite.Title)   }   ## Calling a function inside another function will allow you to make   ## use of variables defined in functions that call it. Normally variable   ## values are only accessible in the scope they were created. We need   ## to pass off $listOfSites to the function GetLIstOfItems so it can process   ## the array   GetListOfItems  }  else  {   ## Gracefully let the user know that the site they requested   ## was not available or was not found.   Write-Host "$web not found, check the url and try again."  } }   function GetListOfItems {  $listWeb = Get-SPWeb $rollupSite  $listName = $listWeb.Lists[$rollupListName]  foreach($rollupListItem in $listName.Items)  {   $listOfItems += @($rollupListItem.Title)  }  CompareItems }   function CompareItems {  foreach($foundSite in $listOfSites)  {   ## Filter out anything that already exists in the Rollup List   ## We have to use -notcontains/-contains when analyizng arrays   if($listOfItems -notcontains $foundSite)   {    ## Item not found so lets create new item    foreach($value in $foundSite)    {     $rollupListWeb = Get-SPWeb $rollupSite     $rollupList = $rollupListWeb.Lists[$rollupListName]     $rollupListItems = $rollupList.Items.Add()     $rollupListItems["Title"] = $value     $rollupListItems.Update()     Write-Host "Creating $value"    }   }   else   {    ## Item was found so lets update it    foreach($value in $foundSite)    {     $rollupListWeb = Get-SPWeb $rollupSite     $rollupList = $rollupListWeb.Lists[$rollupListName]     $rollupListItems = $rollupList.Items           if($rollupListItems.Title  -notmatch $value)     {      $rollupListItem["Title"] = $value      $rollupListItem.Update()      Write-Host "Updating $value"     }    }   }  } } Start-SPAssignment -Global GetListOfSites Stop-SPAssignment -Global