Sitecore fix dynamic placeholder keys

Sitecore-9-Dynamic-placeholder-key-format-fix.ps1

$startPath = "/sitecore/content/home"
$placeholderKey = "*_*"

$outputFilePath = "C:\temp\placeholder-replacement-report.csv"
$results = @();

Write-Progress -Activity "Upgrading dynamic placeholders that for the key [$($placeholderKey)]" `
    -Status "Getting content items"

Get-ChildItem -Path $startPath -Recurse -Version * | ForEach-Object {
    $item = $_;

    Write-Progress -Activity "Upgrading dynamic placeholders that for the key [$($placeholderKey)]" `
        -CurrentOperation "Updating [$($item.Name)]..."

    $itemPath = $_.FullPath
    $itemId = $_.Id
    $version = $_.Version

    Get-Rendering -Item $_ -FinalLayout -Placeholder $placeholderKey | Foreach-Object {
        
        # Double check that this is an old style dynamic placeholder - should have a lowercase guid at the end of the string
        $matches = [regex]::Matches($_.Placeholder,'(_[0-9a-f]{8}[-][0-9a-f]{4}[-][0-9a-f]{4}[-][0-9a-f]{4}[-][0-9a-f]{12})')
        if ($matches.Success) {
            Write-Host "Updating: " $itemPath
            $oldPlaceholderKey = $_.Placeholder
            Write-Host "Old placeholder: " $_.Placeholder

            Foreach($group in $matches.Groups)
            {
                $renderingId = $group.Value
                
                # Replace the old style guid with the new style guid and add the unique number
                # for this upgrade, that will always be 0
                $newPlaceholder = $_.Placeholder.Replace($renderingId, "-{$($renderingId.Replace('_','').ToUpper())}-0")

                $_.Placeholder = $newPlaceholder
            }
            Write-Host "New placeholder: " $_.Placeholder
            
            Set-Rendering -FinalLayout -Item $item -Instance $_
            
            $properties = @{
                ITemID = $itemId
                Version = $version
                ItemPath = $itemPath
                RenderingId = $_.UniqueId
                OldPlaceholderKey = $oldPlaceholderKey
                NewPlaceholderKey = $_.Placeholder
            }
            $results += New-Object psobject -Property $properties
        }
    }
}
$Results | Select-Object ItemId,Version,ItemPath,RenderingId,OldPlaceholderKey,NewPlaceholderKey | Export-Csv -notypeinformation -Path $outputFilePath
Write-Progress -Completed -Activity "Done"