[Q] Does PHP have a negative cache for file stat operations?

PHP Internals folks-- We're doing some performance work in WinCache, and we're finding that some frameworks are...uh...enthusiastically using file_exists(), is_file() and is_dir() functions on files/directories that don't exist. Every. Single. Pageload. Does the PHP stat cache include negative cache entries? If not, why not? Are there any existing extensions that implement a negative cache for file_exists(), is_file(), et. al.? Thank you! --E.