First, see this support article about how Firefox handles PDF files for viewing from the web: <br> https://support.mozilla.org/en-US/kb/different-ways-access-pdf-files-firefox Beyond that, '''php''' isn't directly related to PDF files. Additionally, PHP is interpreted on the server where a the web page is hosted; Firefox has no PHP ti interpret the PHP code. Also, if your issue is with a PDF file that is sitting on your computer you can use '''File > Open...''' or '''{Ctrl + O}''' to allow Firefox access to the PDF file; when your use the Open button in the explorer box to have Firefox deal with that file much like when the PDF file is on a web page. That all said, you posted here from an Android device; for help with "mobile" versions of Firefox -- you posted in the Firefox desktop / laptop forum. I can't help you as I don't even have a smart phone and have no experience with Firefox on "mobile" devices.