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<title>Raise an arbitrary precision number to another, reduced by a specified modulus</title>
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<div class="refnamediv">
<h1 class="refname">bcpowmod</h1>
<p class="verinfo">(PHP 5)</p><p class="refpurpose"><span class="refname">bcpowmod</span> — <span class="dc-title">Raise an arbitrary precision number to another, reduced by a specified modulus</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.bcpowmod-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">string</span> <span class="methodname"><strong>bcpowmod</strong></span>
( <span class="methodparam"><span class="type">string</span> <code class="parameter">$left_operand</code></span>
, <span class="methodparam"><span class="type">string</span> <code class="parameter">$right_operand</code></span>
, <span class="methodparam"><span class="type">string</span> <code class="parameter">$modulus</code></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$scale</code></span>
] )</div>
<p class="para rdfs-comment">
Use the fast-exponentiation method to raise
<em><code class="parameter">left_operand</code></em> to the power
<em><code class="parameter">right_operand</code></em> with respect to the modulus
<em><code class="parameter">modulus</code></em>.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.bcpowmod-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">left_operand</code></em></span>
<dd>
<p class="para">
The left operand, as a string.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">right_operand</code></em></span>
<dd>
<p class="para">
The right operand, as a string.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">modulus</code></em></span>
<dd>
<p class="para">
The modulus, as a string.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">
scale</code></em></span><dd>
<p class="para">This optional parameter is used to set the number
of digits after the decimal place in the result. You can also set the global default scale
for all functions by using <span class="function"><a href="function.bcscale.html" class="function">bcscale()</a></span>.</p></dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.bcpowmod-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the result as a string, or <strong><code>NULL</code></strong> if <em><code class="parameter">modulus</code></em>
is 0.
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.bcpowmod-notes">
<h3 class="title">Notes</h3>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Because this method uses the modulus operation, numbers which are not
positive integers may give unexpected results.
</p>
</p></blockquote>
</div>
<div class="refsect1 examples" id="refsect1-function.bcpowmod-examples">
<h3 class="title">Examples</h3>
<p class="para">
The following two statements are functionally identical. The
<span class="function"><strong>bcpowmod()</strong></span> version however, executes in
less time and can accept larger parameters.
<div class="informalexample">
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$a </span><span style="color: #007700">= </span><span style="color: #0000BB">bcpowmod</span><span style="color: #007700">(</span><span style="color: #0000BB">$x</span><span style="color: #007700">, </span><span style="color: #0000BB">$y</span><span style="color: #007700">, </span><span style="color: #0000BB">$mod</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= </span><span style="color: #0000BB">bcmod</span><span style="color: #007700">(</span><span style="color: #0000BB">bcpow</span><span style="color: #007700">(</span><span style="color: #0000BB">$x</span><span style="color: #007700">, </span><span style="color: #0000BB">$y</span><span style="color: #007700">), </span><span style="color: #0000BB">$mod</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// $a and $b are equal to each other.<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.bcpowmod-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.bcpow.html" class="function" rel="rdfs-seeAlso">bcpow()</a> - Raise an arbitrary precision number to another</span></li>
<li class="member"> <span class="function"><a href="function.bcmod.html" class="function" rel="rdfs-seeAlso">bcmod()</a> - Get modulus of an arbitrary precision number</span></li>
</ul>
</p>
</div>
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