What makes a phar a phar and not a tar or a zip?
PHP Manual

Global Phar bitmapped flags

Here are the bitmapped flags currently recognized by the Phar extension for the global Phar flat bitmap:

Bitmap values recognized
Value Description
0x00010000 If set, this Phar contains a verification signature
0x00001000 If set, this Phar contains at least 1 file that is compressed with zlib compression
0x00002000 If set, this Phar contains at least 1 file that is compressed with bzip compression


What makes a phar a phar and not a tar or a zip?
PHP Manual