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</div><hr /><div id="function.uniqid" class="refentry">
<div class="refnamediv">
<h1 class="refname">uniqid</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">uniqid</span> — <span class="dc-title">Generate a unique ID</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.uniqid-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">string</span> <span class="methodname"><strong>uniqid</strong></span>
([ <span class="methodparam"><span class="type">string</span> <code class="parameter">$prefix</code><span class="initializer"> = ""</span></span>
[, <span class="methodparam"><span class="type">bool</span> <code class="parameter">$more_entropy</code><span class="initializer"> = false</span></span>
]] )</div>
<p class="para rdfs-comment">
Gets a prefixed unique identifier based on the current time in
microseconds.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.uniqid-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">prefix</code></em></span>
<dd>
<p class="para">
Can be useful, for instance, if you generate identifiers
simultaneously on several hosts that might happen to generate the
identifier at the same microsecond.
</p>
<p class="para">
With an empty <em><code class="parameter">prefix</code></em>, the returned string will
be 13 characters long. If <em><code class="parameter">more_entropy</code></em> is
<strong><code>TRUE</code></strong>, it will be 23 characters.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">more_entropy</code></em></span>
<dd>
<p class="para">
If set to <strong><code>TRUE</code></strong>, <span class="function"><strong>uniqid()</strong></span> will add additional
entropy (using the combined linear congruential generator) at the end
of the return value, which increases the likelihood that the result
will be unique.
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.uniqid-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the unique identifier, as a string.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.uniqid-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-3788">
<p><strong>Example #1 <span class="function"><strong>uniqid()</strong></span> Example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">/* A uniqid, like: 4b3403665fea6 */<br /></span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"uniqid(): %s\r\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">uniqid</span><span style="color: #007700">());<br /><br /></span><span style="color: #FF8000">/* We can also prefix the uniqid, this the same as <br /> * doing:<br /> *<br /> * $uniqid = $prefix . uniqid();<br /> * $uniqid = uniqid($prefix);<br /> */<br /></span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"uniqid('php_'): %s\r\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">uniqid</span><span style="color: #007700">(</span><span style="color: #DD0000">'php_'</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">/* We can also activate the more_entropy parameter, which is <br /> * required on some systems, like Cygwin. This makes uniqid()<br /> * produce a value like: 4b340550242239.64159797<br /> */<br /></span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"uniqid('', true): %s\r\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">uniqid</span><span style="color: #007700">(</span><span style="color: #DD0000">''</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.uniqid-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>5.0.0</td>
<td>
The <em><code class="parameter">prefix</code></em> parameter was made optional.
</td>
</tr>
<tr>
<td>4.3.1</td>
<td>
The limit of 114 characters long for <em><code class="parameter">prefix</code></em>
was raised.
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.uniqid-notes">
<h3 class="title">Notes</h3>
<div class="caution"><strong class="caution">Caution</strong>
<p class="para">
This function does not generate cryptographically secure tokens,
in fact without being passed any additional parameters the return
value is little different from <span class="function"><a href="function.microtime.html" class="function">microtime()</a></span>. If
you need to generate cryptographically secure tokens use
<span class="function"><a href="function.openssl-random-pseudo-bytes.html" class="function">openssl_random_pseudo_bytes()</a></span>.
</p>
</div>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Under Cygwin, the <em><code class="parameter">more_entropy</code></em> must be set
to <strong><code>TRUE</code></strong> for this function to work.
</p>
</p></blockquote>
</div>
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