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<title>Seed the random number generator</title>
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<div class="refnamediv">
<h1 class="refname">srand</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">srand</span> — <span class="dc-title">Seed the random number generator</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.srand-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type"><span class="type void">void</span></span> <span class="methodname"><strong>srand</strong></span>
([ <span class="methodparam"><span class="type">int</span> <code class="parameter">$seed</code></span>
] )</div>
<p class="para rdfs-comment">
Seeds the random number generator with <em><code class="parameter">seed</code></em>
or with a random value if no <em><code class="parameter">seed</code></em> is given.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara">As of PHP 4.2.0, there is no need
to seed the random number generator with <span class="function"><strong>srand()</strong></span> or
<span class="function"><a href="function.mt-srand.html" class="function">mt_srand()</a></span> as this is now done automatically.
</span></p></blockquote>
</div>
<div class="refsect1 parameters" id="refsect1-function.srand-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">seed</code></em></span>
<dd>
<p class="para">
Optional seed value
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.srand-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
No value is returned.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.srand-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>4.2.0</td>
<td>
The <em><code class="parameter">seed</code></em> becomes optional
and defaults to a random value if omitted.
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.srand-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-3479">
<p><strong>Example #1 <span class="function"><strong>srand()</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">// seed with microseconds<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">make_seed</span><span style="color: #007700">()<br />{<br /> list(</span><span style="color: #0000BB">$usec</span><span style="color: #007700">, </span><span style="color: #0000BB">$sec</span><span style="color: #007700">) = </span><span style="color: #0000BB">explode</span><span style="color: #007700">(</span><span style="color: #DD0000">' '</span><span style="color: #007700">, </span><span style="color: #0000BB">microtime</span><span style="color: #007700">());<br /> return (float) </span><span style="color: #0000BB">$sec </span><span style="color: #007700">+ ((float) </span><span style="color: #0000BB">$usec </span><span style="color: #007700">* </span><span style="color: #0000BB">100000</span><span style="color: #007700">);<br />}<br /></span><span style="color: #0000BB">srand</span><span style="color: #007700">(</span><span style="color: #0000BB">make_seed</span><span style="color: #007700">());<br /></span><span style="color: #0000BB">$randval </span><span style="color: #007700">= </span><span style="color: #0000BB">rand</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.srand-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.rand.html" class="function" rel="rdfs-seeAlso">rand()</a> - Generate a random integer</span></li>
<li class="member"> <span class="function"><a href="function.getrandmax.html" class="function" rel="rdfs-seeAlso">getrandmax()</a> - Show largest possible random value</span></li>
<li class="member"> <span class="function"><a href="function.mt-srand.html" class="function" rel="rdfs-seeAlso">mt_srand()</a> - Seed the better random number generator</span></li>
</ul>
</p>
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