It seems that the standard PHP module SQLite is not enabled in the "PHP Webserver" repl. This means that you cannot use SQLite. You can upload a SQLite database as file but cannot access.
It would be very handy to at least read from the database – or as with the SQlite repl, have both read and write access.
Is there any chance that you, repl.it, will add SQLite to the PHP Webserver repl?
This would help for beginner tutorials where you introduce simple databases via SQLite.