Wordpress Multi - site Header & Footer Integration with vBulletin 5.0.x

[npadbidri]

Wordpress Multi - site Header & Footer Integration :

Hello,
I'm trying to integrate vBulletin 5.0.x with Wordpress.
Specifically, I'm trying to add the WordPress header and footer to show in vBulletin using Wordpress's functions get_header() and get_footer() that come from the file wp-blog-header.php in the WordPress installation folder. But my Wordpress site is a multi - site and I need header and footer of a particular website.

I have tried Wordpress header & footer integration with vBulletin 5.0.x for single website and It works fine.
I refer this post : Wordpress Header & Footer Integation (https://vborg.vbsupport.ru/showthread.php?t=302307) for Wordpress header & footer integration with vBulletin 5.0.x for single website.

While intergration of Wordpress multi - site header & footer with vBulletin 5.0.x, I got following error :

Fatal error: Call to undefined method stdClass::escape() in \wp-content\sunrise.php.

################################################## ##
PHP code : (written into packages/extension/api/options.php)

<?php

class wpHeaderFooter_Api_Options extends vB_Api_Extensions
{
public $product = 'wpheaderfooter';
public $version = '1.0.0';
public $developer = 'me';
public $title = 'WordPress Integration Extension';
public $minver = '5.0.4';
public $maxver = '5.1.3';
public $infourl = '';
public $checkurl = '';
public $AutoInstall = 1;
public $extensionOrder = 10;

public function wpHeader(){
define('ROOT_DIR',str_replace('\\\\', '/', realpath(dirname(__FILE__))).'/'); #Get real path for root dir ---linux and windows
require_once(ROOT_DIR.'../testsite/wp-blog-header.php'); // get WordPress
get_header();
}

public function wpFooter(){
define('ROOT_DIR',str_replace('\\\\', '/', realpath(dirname(__FILE__))).'/'); #Get real path for root dir ---linux and windows
require_once(ROOT_DIR.'../testsite/wp-blog-header.php'); // get WordPress
get_footer();
}
} So any help would be greatly appreciated.
Thanks!!!:)