zlib, bzip2 and zip — Compression Streams
zlib: PHP 4.0.4 - PHP 4.2.3 (systems with fopencookie only)
compress.zlib:// and compress.bzip2:// PHP 4.3.0 and up
zlib: works like gzopen(), except that the stream can be used with fread() and the other filesystem functions. This is deprecated as of PHP 4.3.0 due to ambiguities with filenames containing ':' characters; use compress.zlib:// instead.
compress.zlib:// and compress.bzip2:// are equivalent to gzopen() and bzopen() respectively, and operate even on systems that do not support fopencookie.
ZIP extension registers zip: wrapper.
I had a difficult time finding how to use compress.zlib with an http resource so I thought I would post what I found
<?php
$file = 'compress.zlib://http://www.example.com/myarchive.gz';
$fr = fopen($file, 'rb');
?>
Per the bugreport I found here (http://bugs.php.net/bug.php?id=29045)