What is the filename used for?

[jesseschalken]

ast\parse_code() accepts an optional $filename parameter but the readme doesn't say what it's for. I tried for follow the code and ended up in zend_set_compiled_filename() which talks about CG(compiled_filename) and CG(filenames_table) but couldn't get much further.

Does the filename affect the output of ast\parse_code() in any way? Is it just used in case of error, perhaps?

[nikic]

At least right now it's used only for errors. We don't resolve __FILE__ with it, or similar.