php-doc-en/reference/math/functions/pow.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.pow" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>pow</refname>
  <refpurpose>Exponential expression</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
   <methodsynopsis>
    <type class="union"><type>int</type><type>float</type></type><methodname>pow</methodname>
    <methodparam><type class="union"><type>int</type><type>float</type></type><parameter>base</parameter></methodparam>
    <methodparam><type class="union"><type>int</type><type>float</type></type><parameter>exp</parameter></methodparam>
   </methodsynopsis>
  <para>
   Returns <parameter>base</parameter> raised to the power of
   <parameter>exp</parameter>. 
  </para>
  <note>
   <para>
    In PHP 5.6 onwards, you may prefer to use the
    <link linkend="language.operators.arithmetic">**</link> operator.
   </para>
  </note>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>base</parameter></term>
     <listitem>
      <para>
       The base to use
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>exp</parameter></term>
     <listitem>
      <para>
       The exponent
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   <parameter>base</parameter> raised to the power of <parameter>exp</parameter>.
   If both arguments are non-negative integers and the result can be represented
   as an integer, the result will be returned with <type>int</type> type,
   otherwise it will be returned as a <type>float</type>.
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>Some examples of <function>pow</function></title>
    <programlisting role="php">
<![CDATA[
<?php

var_dump(pow(2, 8)); // int(256)
echo pow(-1, 20); // 1
echo pow(0, 0); // 1
echo pow(10, -1); // 0.1

echo pow(-1, 5.5); // PHP >=5.2.2: NAN
echo pow(-1, 5.5); // PHP <5.2.2: -NAN
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <note>
   <para>
    This function will convert all input to a number, even non-scalar values,
    which could lead to <literal>weird</literal> results.
   </para>
  </note>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>exp</function></member>
    <member><function>sqrt</function></member>
    <member><function>bcpow</function></member>
    <member><function>gmp_pow</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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