I mentioned USB installed server for PHP in another topic.
They are often called pen drive <- search google.
( there are evenso COMPLETE Linux OS to run on an USB Stick !!!
for example DSL - damn small linux)
Once you have a server (not necessarily apache) working in your USB
and this server can be configured for PHP
... then rest is no problem.
Download and install PHP, too.
For a webserver even so small USB Flash as 256MB is very large.
200 MB webspace is quite enough, for 95% of all apps.
Eventhough I have not tried this,
I can not see any problems with running a SQL database program (.exe or .bin) too.
Then you take your PHP-System Server with you, in your pocket,
and run it on some free port in any PC.
( When the file sharing police come to take you,
you just rip your USB out of PC socket connector,
put it inside your underwear and just give them a big smile! )
🙂