Instead of the default theme, one could imagine having
PHP Shell look like any of the known shells: xterm,
Eterm, Gnometerminal, etc.
This would be a matter of cutting a screenshot of the
wanted terminal up into pieces and then add them to the
PHP Shell could then have a special mode where it
creates a new window with as little browser-specific
stuff as possible so as to look as much as the wanted
shell as possible.