With vdump you can dump all variables in a running PHP process.

It has to be compiled in, and then provides a function vdump_dump($fn) which writes all variables to file $fn.

You can also use GDB to dump a remote process:
$ gdb -p $PID
> set unwindonsignal on
> call vdump_dump_no_tsrm("/tmp/vdump-$PID");
> detach