Rendering page html to a variable

parser = new SidebarParser( $modx->db , $id );
$page = $parser->executeParser();

class SidebarParser extends DocumentParser {

	public $mDocId = "";

    function SidebarParser( $db , $docId ) {
        $this->db = $db;
        $this->mDocId = $docId;
        //echo $this->mDocId;
		$this->dbConfig= & $this->db->config; // alias for backward compatibility
        $this->jscripts= array ();
        $this->sjscripts= array ();
        $this->loadedjscripts= array ();
        // events
        $this->event= new SystemEvent();
        $this->Event= & $this->event; //alias for backward compatibility
        $this->pluginEvent= array ();
        // set track_errors ini variable
        @ ini_set("track_errors", "1"); // enable error tracking in $php_errormsg
    }


	

function getDocumentMethod() {  
		return "id"; 
	} 
	
	function getDocumentIdentifier($method) { 
		return $this->mDocId;  
	}

  

    function prepareResponse() {

	//echo "prepare";

        // we now know the method and identifier, let's check the cache
        $this->documentContent= $this->checkCache($this->documentIdentifier);
        

	//echo "prepare2";

	  /*if ($this->documentContent != "") {
            // invoke OnLoadWebPageCache  event
            $this->invokeEvent("OnLoadWebPageCache");
        } else {*/
            // get document object
            //echo $this->documentMethod . $this->documentIdentifier;

		$this->documentObject= $this->getDocumentObject($this->documentMethod, $this->documentIdentifier);

            // write the documentName to the object
            $this->documentName= $this->documentObject['pagetitle'];

            // validation routines
            if ($this->documentObject['deleted'] == 1) {
                	//echo "error";

			$this->sendErrorPage();
            }

		//echo "template fetch";

            // get the template and start parsing!
            if (!$this->documentObject['template'])
                $this->documentContent= "[*content*]"; // use blank template
            else {
                $sql= "SELECT * FROM " . $this->getFullTableName("site_templates") . " WHERE " . $this->getFullTableName("site_templates") . ".id = '" . $this->documentObject['template'] . "';";
                $result= $this->dbQuery($sql);
                $rowCount= $this->recordCount($result);
                if ($rowCount > 1) {
                    $this->messageQuit("Incorrect number of templates returned from database", $sql);
                }
                elseif ($rowCount == 1) {
                    $row= $this->fetchRow($result);
                    $this->documentContent= $row['content'];
                }
            //}

            // invoke OnLoadWebDocument event
            //$this->invokeEvent("OnLoadWebDocument");

		//echo "before parse";
		//echo $this->documentContent;
            // Parse document source
            $this->documentContent = $this->parseDocumentSource($this->documentContent);
		
		//echo $this->documentContent;

            // setup <base> tag for friendly urls
            //			if($this->config['friendly_urls']==1 && $this->config['use_alias_path']==1) {
            //				$this->regClientStartupHTMLBlock('<base href="'.$this->config['site_url'].'" />');
            //			}
        }
      /*  
	register_shutdown_function(array (
            & $this,
            "postProcess"
        )); // tell PHP to call postProcess when it shuts down
*/
        //$this->outputContent();
        //$this->postProcess();
    }


  function sendForward($id, $responseCode= '') {
        if ($this->forwards > 0) {
            $this->forwards= $this->forwards - 1;
            $this->documentIdentifier= $id;
            $this->documentMethod= 'id';
            $this->documentObject= $this->getDocumentObject('id', $id);
            //if ($responseCode) {
            //    header($responseCode);
            //}
            $this->prepareResponse();
            //exit();
        } else {
            //header('HTTP/1.0 500 Internal Server Error');
            //die('<h1>ERROR: Too many forward attempts!</h1><p>The request could not be completed due to too many unsuccessful forward attempts.</p>');
        }
    }


    function executeParser() {
        //error_reporting(0);
        if (version_compare(phpversion(), "5.0.0", ">="))
            set_error_handler(array (
                & $this,
                "phpError"
            ), E_ALL);
        else
            set_error_handler(array (
                & $this,
                "phpError"
            ));

        $this->db->connect();

        // get the settings
        if (empty ($this->config)) {
            $this->getSettings();
        }

        // IIS friendly url fix
        if ($this->config['friendly_urls'] == 1 && strpos($_SERVER['SERVER_SOFTWARE'], 'Microsoft-IIS') !== false) {
            $url= $_SERVER['QUERY_STRING'];
            $err= substr($url, 0, 3);
            if ($err == '404' || $err == '405') {
                $k= array_keys($_GET);
                unset ($_GET[$k[0]]);
                unset ($_REQUEST[$k[0]]); // remove 404,405 entry
                $_SERVER['QUERY_STRING']= $qp['query'];
                $qp= parse_url(str_replace($this->config['site_url'], '', substr($url, 4)));
                if (!empty ($qp['query'])) {
                    parse_str($qp['query'], $qv);
                    foreach ($qv as $n => $v)
                        $_REQUEST[$n]= $_GET[$n]= $v;
                }
                $_SERVER['PHP_SELF']= $this->config['base_url'] . $qp['path'];
                $_REQUEST['q']= $_GET['q']= $qp['path'];
            }
        }

        // check site settings
	/*        
if (!$this->checkSiteStatus()) {
            header('HTTP/1.0 503 Service Unavailable');
            if (!$this->config['site_unavailable_page']) {
                // display offline message
                $this->documentContent= $this->config['site_unavailable_message'];
                $this->outputContent();
                exit; // stop processing here, as the site's offline
            } else {
                // setup offline page document settings
                $this->documentMethod= "id";
                $this->documentIdentifier= $this->config['site_unavailable_page'];
            }
        } else {*/
            // make sure the cache doesn't need updating
            $this->checkPublishStatus();

            // find out which document we need to display
            $this->documentMethod= $this->getDocumentMethod();
            $this->documentIdentifier= $this->getDocumentIdentifier($this->documentMethod);
        //}

        if ($this->documentMethod == "none") {
            $this->documentMethod= "id"; // now we know the site_start, change the none method to id
        }
        if ($this->documentMethod == "alias") {
            $this->documentIdentifier= $this->cleanDocumentIdentifier($this->documentIdentifier);
        }

        if ($this->documentMethod == "alias") {
            // Check use_alias_path and check if $this->virtualDir is set to anything, then parse the path
            if ($this->config['use_alias_path'] == 1) {
                $alias= (strlen($this->virtualDir) > 0 ? $this->virtualDir . '/' : '') . $this->documentIdentifier;
                if (array_key_exists($alias, $this->documentListing)) {
                    $this->documentIdentifier= $this->documentListing[$alias];
                } else {
                    $this->sendErrorPage();
                }
            } else {
                $this->documentIdentifier= $this->documentListing[$this->documentIdentifier];
            }
            $this->documentMethod= 'id';
        }

        // invoke OnWebPageInit event
        $this->invokeEvent("OnWebPageInit");

        // invoke OnLogPageView event
        if ($this->config['track_visitors'] == 1) {
            $this->invokeEvent("OnLogPageHit");
        }

        $this->prepareResponse();

	return $this->documentContent;
    }



}

<?php
// Get a MODx Resource by id
$resource = $modx->getObject('modResource', 12);

// See modResponse::outputContent() for additional details/ideas
// Process and return the cacheable content of the Resource
$output = $resource->process();

// Determine how many passes the parser should take at a maximum
$maxIterations= intval($modx->getOption('parser_max_iterations', $scriptProperties, 10));

// Process the non-cacheable content of the Resource, but leave any unprocessed tags alone
$modx->parser->processElementTags('', $output, true, false, '[[', ']]', array(), $maxIterations);

// Process the non-cacheable content of the Resource, this time removing the unprocessed tags
$modx->parser->processElementTags('', $output, true, true, '[[', ']]', array(), $maxIterations);

// Use the $output however you like...
?>