This module enables you to transparently read and write gzip (.gz) compressed files, through versions of most of the filesystem functions which work with gzip-compressed files (and uncompressed files, too, but not with sockets).
Note:
Version 4.0.4 introduced a fopen-wrapper for .gz-files, so that you can use a special zlib: URL to access compressed files transparently using the normal f*() file access functions if you prefix the filename or path with zlib: when calling fopen(). This feature requires a C runtime library that provides the fopencookie() function. Up to now the GNU libc seems to be the only library that provides this feature.
In PHP 4.3.0, zlib: has been changed to compress.zlib:// to prevent ambiguities with filenames containing ':' characters. The fopencookie() function is no longer required. More information is available in the section about zlib://.
This introduction is incomplete because it lacks the information that the module can be used to use HTTP gzip compression with the 'zlib.output_compression' and 'zlib.output_compression_level' configuration settings.
Please be aware that cross-site scripting should be disabled when using HTTP compression because of possible BREACH attacks.