FFI::load

Since #include's and #define's other than FFI_LIB and FFI_SCOPE are not supported in the header, you may want to use the C preprocessor to pre-process your headers in order to resolve all #include's and macros.

I use -D"__attribute__(ARGS)=" to remove function attributes as well, which are not supported by FFI either.

This is my script:

echo '#define FFI_SCOPE "YOUR_SCOPE"' > header-ffi.h
echo '#define FFI_LIB "/path/to/your_lib.so"' >> header-ffi.h
cpp -P -C -D"__attribute__(ARGS)=" header_original >> header-ffi.h

Regarding the `FFI_LIB` constant:

The path given can be either relative, or absolute, or then refer to a library that is in your global libraries path (i.e. where libc.so.6 and friends are).

The absolute path and global lib path work as expected. The relative path does not work from the header file path, but the current working directory instead. So when you create header files for FFI usage, remember that the PHP script can be called anywhere and this means any relative paths in `FFI_LIB` will most probably fail.

Not sure if there is some possibility to make it use paths relative to the script being called, or relative to the header file being loaded. That would make more sense to me at least.

Right now `FFI_LIB` is quite unusable when it comes to making FFI-powered PHP packages that can be installed literally anywhere on a system. `FFI::cdef` works just as well, but `FFI::scope` also seems to rely on `FFI_LIB` meaning it will fail with relative paths as well.

I guess this comes from the C function `dlopen` as is.