Tar-based phars
Phar File Format
What makes a phar a phar and not a tar or a zip?
PHP Manual

## 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/

Tar-based phars
Phar File Format
What makes a phar a phar and not a tar or a zip?
PHP Manual