PHP coupled with HTML is the preferred method for displaying feeds on a website when it comes to search engine optimization. This is so because servers use the PHP language to communicate with an HTML website. The search engine spiders do not recognize the PHP, but it recognizes the HTML that PHP initiates and controls via the server.
Search spiders are very ancient in regards to recognizing new markup language technology. One could say search engines are lagging so far behind in terms of markup language interpretation that it is surprising that they still manage to continue functioning. They continue to function because HTML is still the main language used by websites.
The PHP to HTML option of displaying feed content is much more search engine-friendly. When the server communicates to the website, it uses the PHP language to do the communicating. The website then responds to the signals from the server by using the HTML markup language, which is what the search spider seas and can recognize.
The RSS feed is then displayed among the HTML codes and tags where the search engine spiders picks them up and deliver them to the search engine directory for archiving. So when search terms corresponding to those key words are entered into the search engine search bar, the search engine displays the archived information to the human searcher.
The search engine therefore perceives the feed content between the HTML codes on a website displaying feeds as belonging to that website. So even though the content or feed is being fed from another site, the search engine thinks that it originates from the website displaying the RSS feed. This is the advantage of using PHP and HTML to display RSS content on a website.