String replace in Placeholder Keys

ReplacePlaceholderRenderingId.ps1

# String Replace inside Placeholder Keys
$oldPlaceholderString = "da653398-c1bc-4587-be48-0ae26b07ba9e"
$newPlaceholderString = "bfd7aec3-8655-4aff-9357-da7529754aad"
$rootItem = "master:/sitecore/content/MyHome/"
$language = "en"

$defaultLayout = Get-LayoutDevice "Default"
# Toggle for whether to update Shared or Final Layout
$useFinalLayout = $False
# If set to true, the script will only list the renderings that need fixing, rather than fixing them.
$reportOnly = $True

foreach ( $item in Get-ChildItem -Path $rootItem -Recurse -Language $language )
{
    # Only interested in items that have a layout
    if (Get-Layout $item -Device $defaultLayout)
    {
        # Get renderings in this item that have renderings in the placeholder we want to update 
        $renderings =  Get-Rendering -Item $item -Device $defaultLayout -FinalLayout:$useFinalLayout

        foreach ( $rendering in $renderings )
        {
            if ($rendering.Placeholder -match $oldPlaceholderString) 
            {
                $oldPlaceholder = $rendering.Placeholder
                $newPlaceholder = $rendering.Placeholder -replace $oldPlaceholderString, $newPlaceholderString
                
                # Only update the rendering if we're not in "Report Only" mode
                if (!$reportOnly)
                {
                   # Update the placeholder in the rendering and set it back in the item
                   $rendering.Placeholder = $newPlaceholder
                   Set-Rendering -Item $item -Instance $rendering -FinalLayout:$useFinalLayout
                }
                Write-Host "$($item.FullPath) - Rendering $($rendering.UniqueID)"
                Write-Host "    $oldPlaceholder"
                Write-Host "--> $newPlaceholder"
            }
        }        
    }
}