php-doc-en/reference/zlib/functions/gzencode.xml

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<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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