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<title>Initialize an incremental deflate context</title>
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<div class="refnamediv">
<h1 class="refname">deflate_init</h1>
<p class="verinfo">(PHP 7)</p><p class="refpurpose"><span class="refname">deflate_init</span> — <span class="dc-title">Initialize an incremental deflate context</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.deflate-init-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">resource</span> <span class="methodname"><strong>deflate_init</strong></span>
( <span class="methodparam"><span class="type">int</span> <code class="parameter">$encoding</code></span>
[, <span class="methodparam"><span class="type">array</span> <code class="parameter">$options</code><span class="initializer"> = array()</span></span>
] )</div>
<p class="para rdfs-comment">
Initializes an incremental deflate context using the specified
<code class="parameter">encoding</code>.
</p>
<p class="para">
Note that the <em>window</em> option here only sets the window size
of the algorithm, differently from the zlib filters where the same parameter
also sets the encoding to use; the encoding must be set with the
<code class="parameter">encoding</code> parameter.
</p>
<p class="para">
Limitation: there is currently no way to set the header information on a GZIP
compressed stream, which are set as follows: GZIP signature
(<em>\x1f\x8B</em>); compression method (<em>\x08</em>
== DEFLATE); 6 zero bytes; the operating system set to the current system
(<em>\x00</em> = Windows, <em>\x03</em> = Unix, etc.)
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.deflate-init-parameters">
<h3 class="title">Parameters</h3>
<dl>
<dt>
<code class="parameter">encoding</code></dt>
<dd>
<p class="para">
One of the <strong><code>ZLIB_ENCODING_*</code></strong> constants.
</p>
</dd>
<dt>
<code class="parameter">options</code></dt>
<dd>
<p class="para">
An associative array which may contain the following elements:
<dl>
<dt>
<var class="varname"><var class="varname">level</var></var></dt>
<dd>
<p class="para">
The compression level in range -1..9; defaults to -1.
</p>
</dd>
<dt>
<var class="varname"><var class="varname">memory</var></var></dt>
<dd>
<p class="para">
The compression memory level in range 1..9; defaults to 8.
</p>
</dd>
<dt>
<var class="varname"><var class="varname">window</var></var></dt>
<dd>
<p class="para">
The zlib window size (logarithmic) in range 8..15; defaults to 15.
</p>
</dd>
<dt>
<var class="varname"><var class="varname">strategy</var></var></dt>
<dd>
<p class="para">
One of <strong><code>ZLIB_FILTERED</code></strong>,
<strong><code>ZLIB_HUFFMAN_ONLY</code></strong>, <strong><code>ZLIB_RLE</code></strong>,
<strong><code>ZLIB_FIXED</code></strong> or
<strong><code>ZLIB_DEFAULT_STRATEGY</code></strong> (the default).
</p>
</dd>
<dt>
<var class="varname"><var class="varname">dictionary</var></var></dt>
<dd>
<p class="para">
A <span class="type"><a href="language.types.string.html" class="type string">string</a></span> or an <span class="type"><a href="language.types.array.html" class="type array">array</a></span> of <span class="type"><span class="type strings">strings</span></span>
of the preset dictionary (default: no preset dictionary).
</p>
</dd>
</dl>
</p>
</dd>
</dl>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.deflate-init-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns a deflate context resource (<em>zlib.deflate</em>) on
success, or <strong><code>FALSE</code></strong> on failure.
</p>
</div>
<div class="refsect1 errors" id="refsect1-function.deflate-init-errors">
<h3 class="title">Errors/Exceptions</h3>
<p class="para">
If an invalid option is passed to <code class="parameter">options</code> or the
context couldn't be created, an error of level <strong><code>E_WARNING</code></strong>
is generated.
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.deflate-init-seealso">
<h3 class="title">See Also</h3>
<ul class="simplelist">
<li class="member"><span class="function"><a href="function.deflate-add.html" class="function" rel="rdfs-seeAlso">deflate_add()</a> - Incrementally deflate data</span></li>
<li class="member"><span class="function"><a href="function.inflate-init.html" class="function" rel="rdfs-seeAlso">inflate_init()</a> - Initialize an incremental inflate context</span></li>
</ul>
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