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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 328313 $ -->
<refentry xml:id="function.gzencode" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<refnamediv>
<refname>gzencode</refname>
<refpurpose>Create a gzip compressed string</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type>string</type><methodname>gzencode</methodname>
<methodparam><type>string</type><parameter>data</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>level</parameter><initializer>-1</initializer></methodparam>
<methodparam choice="opt"><type>int</type><parameter>encoding_mode</parameter><initializer>FORCE_GZIP</initializer></methodparam>
</methodsynopsis>
<para>
This function returns a compressed version of the input
<parameter>data</parameter> compatible with the output of the
<command>gzip</command> program.
</para>
<para>
For more information on the GZIP file format, see the document:
<link xlink:href="&url.rfc;1952">GZIP file format specification
version 4.3</link> (RFC 1952).
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>data</parameter></term>
<listitem>
<para>
The data to encode.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>level</parameter></term>
<listitem>
<para>
The level of compression. Can be given as 0 for no compression up to 9
for maximum compression. If not given, the default compression level will
be the default compression level of the zlib library.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>encoding_mode</parameter></term>
<listitem>
<para>
The encoding mode. Can be <constant>FORCE_GZIP</constant> (the default)
or <constant>FORCE_DEFLATE</constant>.
</para>
<para>
Prior to PHP 5.4.0, using <constant>FORCE_DEFLATE</constant> results in
a standard zlib deflated string (inclusive zlib headers) after a gzip
file header but without the trailing crc32 checksum.
</para>
<para>
In PHP 5.4.0 and later, <constant>FORCE_DEFLATE</constant> generates
RFC 1950 compliant output, consisting of a zlib header, the deflated
data, and an Adler checksum.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
The encoded string, or &false; if an error occurred.
</para>
</refsect1>
<refsect1 role="changelog">
&reftitle.changelog;
<para>
<informaltable>
<tgroup cols="2">
<thead>
<row>
<entry>&Version;</entry>
<entry>&Description;</entry>
</row>
</thead>
<tbody>
<row>
<entry>5.4.0</entry>
<entry>
<constant>FORCE_DEFLATE</constant> now generates RFC 1950 compliant
output.
</entry>
</row>
<row>
<entry>4.2.0</entry>
<entry>
The <parameter>encoding_mode</parameter> parameter was added
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
The resulting data contains the appropriate headers and data
structure to make a standard .gz file, e.g.:
<example>
<title>Creating a gzip file</title>
<programlisting role="php">
<![CDATA[
<?php
$data = implode("", file("bigfile.txt"));
$gzdata = gzencode($data, 9);
$fp = fopen("bigfile.txt.gz", "w");
fwrite($fp, $gzdata);
fclose($fp);
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>gzdecode</function></member>
<member><function>gzdeflate</function></member>
<member><function>gzinflate</function></member>
<member><function>gzuncompress</function></member>
<member><function>gzcompress</function></member>
<member>
<link xlink:href="&url.rfc;1950">
ZLIB Compressed Data Format Specification (RFC 1950)
</link>
</member>
</simplelist>
</para>
</refsect1>
</refentry>
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