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.