recourse->process() not working as expected in snippet

// process the eletter but leave the placeholders as
$doc = $modx->getObject('modResource', array('id'=>$this->get('resource')));
        
$modx->log(modX::LOG_LEVEL_ERROR,'EletterNewsletter->_createEletter() - Resource: '.$this->get('resource') );
        
$docUrl = preg_replace('/&/', '&', $modx->makeUrl($this->get('resource'), '', '&sending=1', 'full') );
       
$modx->log(modX::LOG_LEVEL_ERROR,'EletterNewsletter->_createEletter() - Resource URL: '.$docUrl );
        
$context = $modx->getObject('modContext', array('key' => $doc->get('context_key')));
$contextUrl = $context->getOption('site_url', $modx->getOption('site_url'));
        unset($context);

// the eletter body/message:
$message = $doc->process();

$modx->makeUrl($url, "", "", "full");

$ch = curl_init(); // Initialize Curl
if ($ch === false) {
    echo "Failed to initialize cURL";
}

@curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
@curl_setopt($ch, CURLOPT_USERAGENT, "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)");
@curl_setopt($ch, CURLOPT_FRESH_CONNECT, 1); // don't use a cached version of the url

$url = 'http://localhost/addons/';

curl_setopt($ch, CURLOPT_URL, $url); // Set CURL options

$resource = curl_exec($ch); // get the page

if (curl_errno($ch)) {
    echo  'cURL error: ' . curl_errno($ch) . " - " . curl_error($ch);
} else {
    $file = 'c:/xampp/htdocs/addons/assets/mycomponents/curltest/doc.html';
    $fp = fopen($file,'w');
    if (! $fp) {
        echo 'Could not open file';
    } else {
        fwrite($fp,$resource);
        fclose($fp);
    }

}

curl_close($ch);