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<title>Generate a random value via the Mersenne Twister Random Number Generator</title>
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<div class="refnamediv">
<h1 class="refname">mt_rand</h1>
<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">mt_rand</span> — <span class="dc-title">Generate a random value via the Mersenne Twister Random Number Generator</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.mt-rand-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">int</span> <span class="methodname"><strong>mt_rand</strong></span>
( <span class="methodparam">void</span>
)</div>
<div class="methodsynopsis dc-description">
<span class="type">int</span> <span class="methodname"><strong>mt_rand</strong></span>
( <span class="methodparam"><span class="type">int</span> <code class="parameter">$min</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$max</code></span>
)</div>
<div class="caution"><strong class="caution">Caution</strong><p class="para">This function does not
generate cryptographically secure values, and should not be used for cryptographic purposes. If you need a
cryptographically secure value, consider using <span class="function"><a href="function.random-int.html" class="function">random_int()</a></span>, <span class="function"><a href="function.random-bytes.html" class="function">random_bytes()</a></span>, or
<span class="function"><a href="function.openssl-random-pseudo-bytes.html" class="function">openssl_random_pseudo_bytes()</a></span> instead.</p></div>
<p class="simpara">
Many random number generators of older libcs
have dubious or unknown characteristics and are slow.
The <span class="function"><strong>mt_rand()</strong></span> function is a drop-in replacement
for the older <span class="function"><a href="function.rand.html" class="function">rand()</a></span>. It uses a random
number generator with known characteristics using the
<a href="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html" class="link external">» Mersenne Twister</a>, which
will produce random numbers four times faster than what the average
libc rand() provides.
</p>
<p class="simpara">
If called without the optional <code class="parameter">min</code>,
<code class="parameter">max</code> arguments <span class="function"><strong>mt_rand()</strong></span>
returns a pseudo-random value between 0 and
<span class="function"><a href="function.mt-getrandmax.html" class="function">mt_getrandmax()</a></span>. If you want a random number
between 5 and 15 (inclusive), for example, use <em>mt_rand(5,
15)</em>.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.mt-rand-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">min</code></dt>
<dd>
<p class="para">
Optional lowest value to be returned (default: 0)
</p>
</dd>
<dt>
<code class="parameter">max</code></dt>
<dd>
<p class="para">
Optional highest value to be returned (default: <span class="function"><a href="function.mt-getrandmax.html" class="function">mt_getrandmax()</a></span>)
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.mt-rand-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
A random integer value between <code class="parameter">min</code> (or 0)
and <code class="parameter">max</code> (or <span class="function"><a href="function.mt-getrandmax.html" class="function">mt_getrandmax()</a></span>, inclusive),
or <strong><code>FALSE</code></strong> if <code class="parameter">max</code> is less than <code class="parameter">min</code>.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.mt-rand-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="function"><strong>mt_rand()</strong></span> <a href="migration72.incompatible.html#migration72.incompatible.rand-mt_rand-output" class="link">has received a bug fix</a> for a modulo bias bug. This means that sequences generated with a specific seed may differ from PHP 7.1 on 64-bit machines.
</td>
</tr>
<tr>
<td>7.1.0</td>
<td>
<span class="function"><a href="function.rand.html" class="function">rand()</a></span> <a href="migration71.incompatible.html#migration71.incompatible.rand-srand-aliases" class="link">has been made</a> an alias of <span class="function"><strong>mt_rand()</strong></span>.
</td>
</tr>
<tr>
<td>7.1.0</td>
<td>
<span class="function"><strong>mt_rand()</strong></span> <a href="migration71.incompatible.html#migration71.incompatible.fixes-to-mt_rand-algorithm" class="link">has been updated</a> to use the fixed, correct, version of
the Mersenne Twister algorithm. To fall back to the old behaviour, use <span class="function"><a href="function.mt-srand.html" class="function">mt_srand()</a></span> with <strong><code>MT_RAND_PHP</code></strong> as the second paramter.
</td>
</tr>
<tr>
<td>5.3.4</td>
<td>
Issues an <strong><code>E_WARNING</code></strong> and returns <strong><code>FALSE</code></strong> if
<code class="parameter">max</code> < <code class="parameter">min</code>.
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.mt-rand-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-4263">
<p><strong>Example #1 <span class="function"><strong>mt_rand()</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: #007700">echo </span><span style="color: #0000BB">mt_rand</span><span style="color: #007700">() . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br />echo </span><span style="color: #0000BB">mt_rand</span><span style="color: #007700">() . </span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br />echo </span><span style="color: #0000BB">mt_rand</span><span style="color: #007700">(</span><span style="color: #0000BB">5</span><span style="color: #007700">, </span><span style="color: #0000BB">15</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
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
1604716014
1478613278
6
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.mt-rand-notes">
<h3 class="title">Notes</h3>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
<code class="parameter">min</code> <code class="parameter">max</code> range must
be within the range <span class="function"><a href="function.mt-getrandmax.html" class="function">mt_getrandmax()</a></span>. i.e. (<code class="parameter">max</code> -
<code class="parameter">min</code>) <= <span class="function"><a href="function.mt-getrandmax.html" class="function">mt_getrandmax()</a></span>
Otherwise, <span class="function"><strong>mt_rand()</strong></span> may return poorer random numbers
than it should.
</p>
</div>
</div>
<div class="refsect1 seealso" id="refsect1-function.mt-rand-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><span class="function"><a href="function.mt-srand.html" class="function" rel="rdfs-seeAlso">mt_srand()</a> - Seeds the Mersenne Twister Random Number Generator</span></li>
<li class="member"><span class="function"><a href="function.mt-getrandmax.html" class="function" rel="rdfs-seeAlso">mt_getrandmax()</a> - Show largest possible random value</span></li>
<li class="member"><span class="function"><a href="function.random-int.html" class="function" rel="rdfs-seeAlso">random_int()</a> - Generates cryptographically secure pseudo-random integers</span></li>
<li class="member"><span class="function"><a href="function.random-bytes.html" class="function" rel="rdfs-seeAlso">random_bytes()</a> - Generates cryptographically secure pseudo-random bytes</span></li>
<li class="member"><span class="function"><a href="function.openssl-random-pseudo-bytes.html" class="function" rel="rdfs-seeAlso">openssl_random_pseudo_bytes()</a> - Generate a pseudo-random string of bytes</span></li>
<li class="member"><span class="function"><a href="function.rand.html" class="function" rel="rdfs-seeAlso">rand()</a> - Generate a random integer</span></li>
</ul>
</p>
</div>
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