archived-doc-en/reference/math/constants.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<appendix xml:id="math.constants" xmlns="http://docbook.org/ns/docbook">
 &reftitle.constants;
 &extension.constants.core;
 <!-- TODO: Use MathML the moment PhD supports it -->
 <variablelist>
  <title>Mathematical Constants</title>
  <varlistentry xml:id="constant.m-pi">
   <term>
    <constant>M_PI</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of the number π (pi).
     (<literal>3.14159265358979323846</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-e">
   <term>
    <constant>M_E</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of Euler's number <literal>e</literal>
     (<literal>2.7182818284590452354</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-log2e">
   <term>
    <constant>M_LOG2E</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>log<subscript>2</subscript>(e)</literal>
     (<literal>1.4426950408889634074</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-log10e">
   <term>
    <constant>M_LOG10E</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>log<subscript>10</subscript>(e)</literal>
     (<literal>0.43429448190325182765</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-ln2">
   <term>
    <constant>M_LN2</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>ln(2)</literal>
     (<literal>0.69314718055994530942</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-ln10">
   <term>
    <constant>M_LN10</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>ln(10)</literal>
     (<literal>2.30258509299404568402</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-pi-2">
   <term>
    <constant>M_PI_2</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>π/2</literal>
     (<literal>1.57079632679489661923</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-pi-4">
   <term>
    <constant>M_PI_4</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>π/4</literal>
     (<literal>0.78539816339744830962</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-1-pi">
   <term>
    <constant>M_1_PI</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>1/π</literal>
     (<literal>0.31830988618379067154</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-2-pi">
   <term>
    <constant>M_2_PI</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>2/π</literal>
     (<literal>0.63661977236758134308</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-sqrtpi">
   <term>
    <constant>M_SQRTPI</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>sqrt(π)</literal>
     (<literal>1.77245385090551602729</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-2-sqrtpi">
   <term>
    <constant>M_2_SQRTPI</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>2/sqrt(π)</literal>
     (<literal>1.12837916709551257390</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-sqrt2">
   <term>
    <constant>M_SQRT2</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>sqrt(2)</literal>
     (<literal>1.41421356237309504880</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-sqrt3">
   <term>
    <constant>M_SQRT3</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>sqrt(3)</literal>
     (<literal>1.73205080756887729352</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-sqrt1-2">
   <term>
    <constant>M_SQRT1_2</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>1/sqrt(2)</literal>
     (<literal>0.70710678118654752440</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-lnpi">
   <term>
    <constant>M_LNPI</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of <literal>ln(π)</literal>
     (<literal>1.14472988584940017414</literal>).
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.m-euler">
   <term>
    <constant>M_EULER</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Approximation of Euler's constant γ
     (<literal>0.57721566490153286061</literal>).
    </simpara>
   </listitem>
  </varlistentry>
 </variablelist>

 <variablelist>
  <title>IEEE 754 floating point constants</title>
  <varlistentry xml:id="constant.nan">
   <term>
    <constant>NAN</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Not A Number
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.inf">
   <term>
    <constant>INF</constant>
    (<type>float</type>)
   </term>
   <listitem>
    <simpara>
     Infinity
    </simpara>
   </listitem>
  </varlistentry>
 </variablelist>

 <variablelist>
  <title>Rounding constants</title>
  <note>
   <simpara>
    As of PHP 8.4.0, it is recommended to use the
    <!-- <enumname>RoundingMode</enumname> -->
    RoundingMode
    enum instead.
   </simpara>
  </note>
  <varlistentry xml:id="constant.php-round-half-up">
   <term>
    <constant>PHP_ROUND_HALF_UP</constant>
    (<type>int</type>)
   </term>
   <listitem>
    <simpara>
     Rounding half away from zero.
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.php-round-half-down">
   <term>
    <constant>PHP_ROUND_HALF_DOWN</constant>
    (<type>int</type>)
   </term>
   <listitem>
    <simpara>
     Rounding half toward zero.
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.php-round-half-even">
   <term>
    <constant>PHP_ROUND_HALF_EVEN</constant>
    (<type>int</type>)
   </term>
   <listitem>
    <simpara>
     Round halves to even numbers
    </simpara>
   </listitem>
  </varlistentry>
  <varlistentry xml:id="constant.php-round-half-odd">
   <term>
    <constant>PHP_ROUND_HALF_ODD</constant>
    (<type>int</type>)
   </term>
   <listitem>
    <simpara>
     Round halves to odd numbers
    </simpara>
   </listitem>
  </varlistentry>
 </variablelist>
</appendix>
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