Information parsing. Problem

Question

ASP.NET

Hello.
There is a site. For educational purposes, I'm trying to learn how to parse. Link - goo.gl/MOCHts
It turns out to get the first 11 pages of results.
POST request to go to a specific page:
'__EVENTTARGET' : 'ctl00$ctl00$MainContent$ContentPlaceHolderMiddle$ctl00$SearchResult2$ctl01$ctl(............)' number from 01 in brackets up to 11.
When sending a POST request with the number 12, information is displayed from the 1st page.
Those. the navigation structure for page navigation is as follows:
1 - ctl00$ctl00$MainContent$ContentPlaceHolderMiddle$ctl00$SearchResult2$ctl01$ctl01
2 - ctl00$ctl00$MainContent$ContentPlaceHolderMiddle$ctl00$SearchResult2$ctl01$ctl02
3 - ctl00$ctl00$MainContent$ContentPlaceHolderMiddle$ctl00$SearchResult2$ctl01$ctl03
...
10 - ctl00$ctl00$MainContent$ContentPlaceHolderMiddle$ctl00$SearchResult2$ctl01$ctl10
>> - ctl00$ctl00$MainContent$ContentPlaceHolderMiddle$ SearchResult2$ctl01$ctl11
By clicking on ">>" we go to a page with new numbers, and the queries remain the same!
<< - ctl00$ctl00$MainContent$ContentPlaceHolderMiddle$ctl00$SearchResult2$ctl01$ctl01
11 - ctl00$ctl00$MainContent$ContentPlaceHolderMiddle$ctl00$SearchResult2$ctl01$ctl02
...
20 - ctl00$ctl00$MainContenter$ContentPlaceHolder$ SearchResult2$ctl01$ctl11
21 - ctl00$ctl00$MainContent$ContentPlaceHolderMiddle$ctl00$SearchResult2$ctl01$ctl12
I just can't understand how the site determines that it is already on 20 pages or 50, or some other.
Viewed cookies, POST requests, even header. Everything seems to be the same, with the first 10 results, with the subsequent tens.

Answer 1

Maybe $_SESSION ?