Linux – How to track all files accessed by a process?

lsof:

Try doing this as a starter :

lsof -p <PID>

this command will list all currently open files, fd, sockets for the process with the passed process ID.

For your special needs, see what I can offer as a solution to monitor a php script :

php foo.php & _pid=$!
lsof -r1 -p $_pid
kill %1 # if you want to kill php script

strace:

I recommend the use of strace. Unlike lsof, it stays running for as long as the process is running. It will print out which syscalls are being called when they are called. -e trace=file filters only for syscalls that access the filesystem:

sudo strace -f -t -e trace=file php foo.php

or for an already running process :

sudo strace -f -t -e trace=file -p <PID>