A quick template copying script using postmark-php.

copy-templates.php

<?php
    // You should have already installed wildbit/postmark-php via Composer.
    // This script should be run from the root directory where the 'vendor' 
    // folder is created by Composer.
    require_once('./vendor/autoload.php');

    use Postmark\PostmarkClient;
    use Postmark\Models\PostmarkException;

    try{
        // Pay special attention to  the Server source and destination tokens here:
        $sourceClient = new PostmarkClient('<source server token>');
        $destinationClient = new PostmarkClient('<destination server token>');
        $allTemplates = $sourceClient->listTemplates(300)->templates;
        foreach($allTemplates as $template){
            $templateContent = $sourceClient->getTemplate($template->templateid);
            $destinationClient->createTemplate($templateContent->name, $templateContent->subject, $templateContent->htmlbody, $templateContent->textbody);
            echo "Copied `$templateContent->name`\r\n";
        }

    }catch(PostmarkException $ex){
        echo $ex->httpStatusCode;
        echo $ex->message;
        echo $ex->postmarkApiErrorCode;

    }catch(Exception $generalException){
        echo "Something bad happened, but probably not an issue with Postmark. $generalException";
    }
?>