Php, getInstanceByName

[gintare]

I am following the book "https://www.packtpub.com/":
https://www.packtpub.com/web-development/cms-design-using-php-and-jquery

On chapter one the give simple CMS example.

I am not able to understand the line:
$r=Page::getInstanceByName($page);

From where the method "getInstanceByName" is called?
I could not find such a method in the official Php documentation:
http://php.net/manual-lookup.php?pattern=getInstanceByName&scope=quickre f

<?php
//  index.php
// { common variables and functions
include_once('ww.incs/common.php');
$page=isset($_REQUEST['page'])?$_REQUEST['page']:'';
$id=isset($_REQUEST['id'])?(int)$_REQUEST['id']:0;
 
// }
 
// { get current page id
if(!$id){
    if($page){ // load by name
        $r=Page::getInstanceByName($page);
        if($r && isset($r->id))$id=$r->id;
    }
    if(!$id){ // else load by special
        $special=1;
        if(!$page){
            $r=Page::getInstanceBySpecial($special);
            if($r && isset($r->id))$id=$r->id;
        }
    }
}

The example code also throws error on windows Apache, but i am not dealing with them now. Please find CMS files enclosed.

[gintare]

I am sorry. Seems i become tired. The method "getInstanceByName" exists in the class:
C:\Bitnami\wampstack-5.4.38-0\apache2\htdocs\cms\ww.php_classes\Page.php