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<title>Unpack data from binary string</title>
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<div class="refnamediv">
<h1 class="refname">unpack</h1>
<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">unpack</span> — <span class="dc-title">Unpack data from binary string</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.unpack-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">array</span> <span class="methodname"><strong>unpack</strong></span>
( <span class="methodparam"><span class="type">string</span> <code class="parameter">$format</code></span>
, <span class="methodparam"><span class="type">string</span> <code class="parameter">$data</code></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$offset</code><span class="initializer"> = 0</span></span>
] )</div>
<p class="para rdfs-comment">
Unpacks from a binary string into an array according to the given
<code class="parameter">format</code>.
</p>
<p class="para">
The unpacked data is stored in an associative array. To
accomplish this you have to name the different format codes and
separate them by a slash /. If a repeater argument is present,
then each of the array keys will have a sequence number behind
the given name.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.unpack-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">format</code></dt>
<dd>
<p class="para">
See <span class="function"><a href="function.pack.html" class="function">pack()</a></span> for an explanation of the format codes.
</p>
</dd>
<dt>
<code class="parameter">data</code></dt>
<dd>
<p class="para">
The packed data.
</p>
</dd>
<dt>
<code class="parameter">offset</code></dt>
<dd>
<p class="para">
The offset to begin unpacking from.
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.unpack-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns an associative array containing unpacked elements of binary
string.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.unpack-changelog">
<h3 class="title">Changelog</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>7.2.0</td>
<td>
<span class="type"><a href="language.types.float.html" class="type float">float</a></span> and <span class="type"><a href="language.types.float.html" class="type double">double</a></span> types supports both Big Endian and Little Endian.
</td>
</tr>
<tr>
<td>7.1.0</td>
<td>
The optional <code class="parameter">offset</code> has been added.
</td>
</tr>
<tr>
<td>5.5.0</td>
<td>
<p class="para">
Changes were made to bring this function into line with Perl:
</p>
<p class="para">
The "a" code now retains trailing NULL bytes.
</p>
<p class="para">
The "A" code now strips all trailing ASCII whitespace (spaces, tabs,
newlines, carriage returns, and NULL bytes).
</p>
<p class="para">
The "Z" code was added for NULL-padded strings, and removes trailing
NULL bytes.
</p>
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.unpack-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-4681">
<p><strong>Example #1 <span class="function"><strong>unpack()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$binarydata </span><span style="color: #007700">= </span><span style="color: #DD0000">"\x04\x00\xa0\x00"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$array </span><span style="color: #007700">= </span><span style="color: #0000BB">unpack</span><span style="color: #007700">(</span><span style="color: #DD0000">"cchars/nint"</span><span style="color: #007700">, </span><span style="color: #0000BB">$binarydata</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
[chars] => 4
[int] => 160
)
</pre></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-4682">
<p><strong>Example #2 <span class="function"><strong>unpack()</strong></span> example with a repeater</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$binarydata </span><span style="color: #007700">= </span><span style="color: #DD0000">"\x04\x00\xa0\x00"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$array </span><span style="color: #007700">= </span><span style="color: #0000BB">unpack</span><span style="color: #007700">(</span><span style="color: #DD0000">"c2chars/nint"</span><span style="color: #007700">, </span><span style="color: #0000BB">$binarydata</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Array
(
[chars1] => 4
[chars2] => 0
[int] => 40960
)
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.unpack-notes">
<h3 class="title">Notes</h3>
<div class="caution"><strong class="caution">Caution</strong>
<p class="para">
Note that PHP internally stores integral values as signed. If you
unpack a large unsigned long and it is of the same size as PHP
internally stored values the result will be a negative number
even though unsigned unpacking was specified.
</p>
</div>
<div class="caution"><strong class="caution">Caution</strong>
<p class="para">
If you do not name an element, numeric indices starting from <em>1</em> are used.
Be aware that if you have more than one unnamed element, some data is
overwritten because the numbering restarts from <em>1</em> for each element.
</p>
<p class="para">
<div class="example" id="example-4683">
<p><strong>Example #3 <span class="function"><strong>unpack()</strong></span> example with unnamed keys</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$binarydata </span><span style="color: #007700">= </span><span style="color: #DD0000">"\x32\x42\x00\xa0"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$array </span><span style="color: #007700">= </span><span style="color: #0000BB">unpack</span><span style="color: #007700">(</span><span style="color: #DD0000">"c2/n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$binarydata</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(2) {
[1]=>
int(160)
[2]=>
int(66)
}
</pre></div>
</div>
<div class="example-contents"><p>
Note that the
first value from the <em>c</em> specifier is
overwritten by the first value from the <em>n</em>
specifier.
</p></div>
</div>
</p>
</div>
</div>
<div class="refsect1 seealso" id="refsect1-function.unpack-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><span class="function"><a href="function.pack.html" class="function" rel="rdfs-seeAlso">pack()</a> - Pack data into binary string</span></li>
</ul>
</p>
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