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<title>Introduction</title>
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<h1 class="title">Introduction</h1>
<p class="para">
This module enables you to transparently read and write
gzip (.gz) compressed files, through versions of most of
the <a href="book.filesystem.html" class="link">filesystem</a> functions
which work with gzip-compressed files (and uncompressed files,
too, but not with sockets).
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Version 4.0.4 introduced a fopen-wrapper for <var class="filename">.gz</var>-files, so that
you can use a special <var class="filename">zlib:</var> URL to access
compressed files transparently using the normal f*() file access
functions if you prefix the filename or path with
<var class="filename">zlib:</var> when calling <span class="function"><a href="function.fopen.html" class="function">fopen()</a></span>. This
feature requires a C runtime library that provides the
<em>fopencookie()</em> function. Up to now the GNU libc
seems to be the only library that provides this feature.
</p>
<p class="para">
In PHP 4.3.0, <var class="filename">zlib:</var> has been changed to
<var class="filename">compress.zlib://</var> to prevent ambiguities with
filenames containing '<em>:</em>' characters. The
<em>fopencookie()</em> function is no longer required.
More information is available in the section about
<a href="wrappers.compression.html" class="xref">zlib://</a>.
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