If the website has a javascript scrolling effect that load more content, you can't easily do it in PHP.
One possibility is to inspect the ajax call and simulate that in PHP to obtain the other results.
To do so you could open your browser developer tools, go to the network tab, and filter by xhr.
Now when you scroll and it loads the content, you can see in the developer tools the ajax call that is being made, with the link, the method and the parameters passed.
Making the same call within your PHP script will obtain the same data.
You can see this answers to obtain more detailed instructions:
Request Monitoring in Chrome
In Firefox, how do I see HTTP request headers? (where in web console?)