<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Initialize an incremental hashing context</title>
</head>
<body><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="function.hash-hmac.html">hash_hmac</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.hash-pbkdf2.html">hash_pbkdf2</a></div>
<div class="up"><a href="ref.hash.html">Hash Functions</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div><hr /><div id="function.hash-init" class="refentry">
<div class="refnamediv">
<h1 class="refname">hash_init</h1>
<p class="verinfo">(PHP 5 >= 5.1.2, PECL hash >= 1.1)</p><p class="refpurpose"><span class="refname">hash_init</span> — <span class="dc-title">Initialize an incremental hashing context</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.hash-init-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">resource</span> <span class="methodname"><strong>hash_init</strong></span>
( <span class="methodparam"><span class="type">string</span> <code class="parameter">$algo</code></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$options</code><span class="initializer"> = 0</span></span>
[, <span class="methodparam"><span class="type">string</span> <code class="parameter">$key</code><span class="initializer"> = <strong><code>NULL</code></strong></span></span>
]] )</div>
</div>
<div class="refsect1 parameters" id="refsect1-function.hash-init-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">algo</code></em></span>
<dd>
<p class="para">
Name of selected hashing algorithm (i.e. "md5", "sha256", "haval160,4", etc..). For a list of supported algorithms see <span class="function"><a href="function.hash-algos.html" class="function">hash_algos()</a></span>.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">options</code></em></span>
<dd>
<p class="para">
Optional settings for hash generation, currently supports only one option:
<strong><code>HASH_HMAC</code></strong>. When specified, the <em><code class="parameter">key</code></em>
<em class="emphasis">must</em> be specified.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">key</code></em></span>
<dd>
<p class="para">
When <strong><code>HASH_HMAC</code></strong> is specified for <em><code class="parameter">options</code></em>,
a shared secret key to be used with the HMAC hashing method must be supplied in this
parameter.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.hash-init-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns a Hashing Context resource for use with <span class="function"><a href="function.hash-update.html" class="function">hash_update()</a></span>,
<span class="function"><a href="function.hash-update-stream.html" class="function">hash_update_stream()</a></span>, <span class="function"><a href="function.hash-update-file.html" class="function">hash_update_file()</a></span>,
and <span class="function"><a href="function.hash-final.html" class="function">hash_final()</a></span>.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.hash-init-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-834">
<p><strong>Example #1 Incremental hashing example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$ctx </span><span style="color: #007700">= </span><span style="color: #0000BB">hash_init</span><span style="color: #007700">(</span><span style="color: #DD0000">'md5'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">hash_update</span><span style="color: #007700">(</span><span style="color: #0000BB">$ctx</span><span style="color: #007700">, </span><span style="color: #DD0000">'The quick brown fox '</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">hash_update</span><span style="color: #007700">(</span><span style="color: #0000BB">$ctx</span><span style="color: #007700">, </span><span style="color: #DD0000">'jumped over the lazy dog.'</span><span style="color: #007700">);<br />echo </span><span style="color: #0000BB">hash_final</span><span style="color: #007700">(</span><span style="color: #0000BB">$ctx</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>
5c6ffbdd40d9556b73a21e63c3e0e904
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.hash-init-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.hash.html" class="function" rel="rdfs-seeAlso">hash()</a> - Generate a hash value (message digest)</span></li>
<li class="member"> <span class="function"><a href="function.hash-algos.html" class="function" rel="rdfs-seeAlso">hash_algos()</a> - Return a list of registered hashing algorithms</span></li>
<li class="member"> <span class="function"><a href="function.hash-file.html" class="function" rel="rdfs-seeAlso">hash_file()</a> - Generate a hash value using the contents of a given file</span></li>
<li class="member"> <span class="function"><a href="function.hash-hmac.html" class="function" rel="rdfs-seeAlso">hash_hmac()</a> - Generate a keyed hash value using the HMAC method</span></li>
<li class="member"> <span class="function"><a href="function.hash-hmac-file.html" class="function" rel="rdfs-seeAlso">hash_hmac_file()</a> - Generate a keyed hash value using the HMAC method and the contents of a given file</span></li>
</ul>
</p>
</div>
</div><hr /><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="function.hash-hmac.html">hash_hmac</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.hash-pbkdf2.html">hash_pbkdf2</a></div>
<div class="up"><a href="ref.hash.html">Hash Functions</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div></body></html>
