PHPShell is foremost a pet project I make in late evenings. It is also a wannabe shell for your browser based on PHP, it is compact and comes in a single file (So you could use it for PoC pentesting etc. but seriously, there is better stuff out there)
While PHP-shell technically isnt an interactive shell it does have somewhat interactive support
PHP-shell has a very simple addon system. Take a look at the example addons in the addons/ folder. You basicly just register PHP callables (eg. functions) with the function registerCommand() and voila they are listed in the help command and are usable through the shell interface.
Well thats unfortunate, maybe take a look at the phpshell-config.php. If interactive doesnt work try changing mode with xsetmode shell_exec. If everything else fails, then please do feel free to create an issue regarding your problem.