Zip-based phars

Archives based on the zip file format support
several features built into the zip file format. Per-file and
whole-archive metadata is stored in the zip file comment and zip
archive comment as a serialized string. Pre-existing zip comments
will be successfully read as a string. Per-file compression
read/write is supported with zlib compression, and read access is
supported with bzip2 compression. There is no limit on the number
of files within a zip-based phar archive. Empty directories are
stored in the zip archive as files with a trailing slash like
my/directory/