Add columns into content type from parent content type using csom PowerShell

AddFieldFromParentContentType.ps1

function AddFieldFromParentContentType()
{
    param(
        [Parameter(Mandatory=$true)][string]$url,
        [Parameter(Mandatory=$false)][System.Net.NetworkCredential]$credentials,
        [Parameter(Mandatory=$true)][string]$ContentTypeName,
        [Parameter(Mandatory=$true)][string]$FieldInternalName
    )
    
    begin{
        try
        {
            #Get Client Object
            #
            $Context = New-Object Microsoft.SharePoint.Client.ClientContext($url) 
            $Context.Credentials = $Credentials 

            #Load web object
            #
            $web = $Context.Web
            $fields = $web.Fields;         
            $site = $context.Site 
            $Context.Load($web)
            $Context.Load($site)
            $Context.Load($fields)
            $Context.ExecuteQuery()

        }
        catch
        {
            Write-Host "Error while getting context. Error -->> "  + $_.Exception.Message -ForegroundColor Red
        }
    }
    process{
        try
        {
            #Get content type collections from root web
            #
            $contentTypes = $Context.Site.RootWeb.ContentTypes
            $Context.Load($contentTypes)
            $Context.ExecuteQuery()

            #Get the desired content type from collection
            #
            $contentType = $contentTypes | Where {$_.Name -eq $ContentTypeName}

            #Get parent content type
            #
            $parentContentType = $contentType.Parent
            $Context.Load($parentContentType)
            $Context.ExecuteQuery()

            #Get fields of parent content type
            #
            $fieldCollection = $parentContentType.Fields
            $Context.Load($fieldCollection);
            $Context.ExecuteQuery();

            #Check if field exists in parent content type
            #
            $IsFieldExists = $false
            foreach($fld in $fieldCollection)
            {
                if($fld.get_InternalName() -eq $FieldInternalName){
                    $IsFieldExists = $true
                    $fieldToAdd = $fld
                }
            }
            

            if($IsFieldExists -eq $true)
            {
                #Get all the columns associated with content type
                #
                $fieldRefCollection = $contentType.Fields;
                $Context.Load($fieldRefCollection);
                $Context.ExecuteQuery();

                #Check if field exists in content type
                #
                $IsFieldInContentTypeExists = $false
                foreach($fldInCT in $fieldRefCollection)
                {
                    if($fldInCT.get_InternalName() -eq $fieldToAdd.InternalName){
                        $IsFieldInContentTypeExists = $true
                    }
                }

                if($IsFieldInContentTypeExists -eq $false) {
                    #Add a new column to the content type
                    #
                    $fieldReferenceLink = New-Object Microsoft.SharePoint.Client.FieldLinkCreationInformation
                    $fieldReferenceLink.Field = $fieldToAdd;
                    $contentType.FieldLinks.Add($fieldReferenceLink);
                    
                    $contentType.Update($true)
                    $Context.Load($contentType)
                    $Context.ExecuteQuery()
                    
                    Write-Host "Field" $FieldInternalName "from parent content type added successfully" -ForegroundColor Green
                    Write-Host ""
                }
                else {
                    Write-Host "Field in content type" $contentType.Name "already exists"  -ForegroundColor Green
                    Write-Host ""
                }
            }
            else
            {
                Write-Host "Field" $FieldInternalName "in parent content type" $parent.Name "do not exists" -ForegroundColor Cyan
                Write-Host ""
            }
        }
        catch
        {
            Write-Host ("Error while adding field in contet type. Error -->> " + $_.Exception.Message) -ForegroundColor Red
        }
    }
    end{
        $Context.Dispose()
    }
}