Requirements

Phar requires PHP 5.2.0 or newer. Additional
features require the SPL
extension in order to take advantage of iteration and array access
to a Phar’s file contents. The phar stream does not
require any additional extensions to function.

You may optionally wish to enable the zlib and bzip2 extensions to take
advantage of compressed phar support. In addition, to take
advantage of OpenSSL signing, the OpenSSL extension must be enabled.

Note that a bug in the zlib.deflate stream
filter fixed in PHP version 5.2.6 and newer may cause truncation of
gzip and bzip2-compressed phar archives.

PHP 5.3 configured with
–enable-zend-multibyte makes phar dependant on the ini option
detect_unicode.