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

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<appendix xml:id="math.constants" xmlns="http://docbook.org/ns/docbook">
 &reftitle.constants;
 &extension.constants.core;
 <para>
  <table>
   <title>Math constants</title>
   <tgroup cols="4">
    <thead>
     <row>
      <entry>Constant</entry>
      <entry>Value</entry>
      <entry>Description</entry>
      <entry>Availability</entry>
     </row>
    </thead>
    <tbody>
     <row xml:id="constant.m-pi">
      <entry><constant>M_PI</constant></entry>
      <entry>3.14159265358979323846</entry>
      <entry>Pi</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-e">
      <entry><constant>M_E</constant></entry>
      <entry>2.7182818284590452354</entry>
      <entry>e</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-log2e">
      <entry><constant>M_LOG2E</constant></entry> 
      <entry>1.4426950408889634074</entry>
      <entry>log_2 e</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-log10e">
      <entry><constant>M_LOG10E</constant></entry>
      <entry>0.43429448190325182765</entry>
      <entry>log_10 e</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-ln2">
      <entry><constant>M_LN2</constant></entry>   
      <entry>0.69314718055994530942</entry>
      <entry>log_e 2</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-ln10">
      <entry><constant>M_LN10</constant></entry>  
      <entry>2.30258509299404568402</entry>
      <entry>log_e 10</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-pi-2">
      <entry><constant>M_PI_2</constant></entry>
      <entry>1.57079632679489661923</entry>
      <entry>pi/2</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-pi-4">
      <entry><constant>M_PI_4</constant></entry>
     <entry>0.78539816339744830962</entry>
      <entry>pi/4</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-1-pi">
      <entry><constant>M_1_PI</constant></entry>
      <entry>0.31830988618379067154</entry>
      <entry>1/pi</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-2-pi">
      <entry><constant>M_2_PI</constant></entry>
      <entry>0.63661977236758134308</entry>
      <entry>2/pi</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-sqrtpi">
      <entry><constant>M_SQRTPI</constant></entry>    
      <entry>1.77245385090551602729</entry>
      <entry>sqrt(pi)</entry>
      <entry>PHP 5.2.0</entry>
     </row>
     <row xml:id="constant.m-2-sqrtpi">
      <entry><constant>M_2_SQRTPI</constant></entry>  
      <entry>1.12837916709551257390</entry>
      <entry>2/sqrt(pi)</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-sqrt2">
      <entry><constant>M_SQRT2</constant></entry> 
      <entry>1.41421356237309504880</entry>
      <entry>sqrt(2)</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-sqrt3">
      <entry><constant>M_SQRT3</constant></entry> 
      <entry>1.73205080756887729352</entry>
      <entry>sqrt(3)</entry>
      <entry>PHP 5.2.0</entry>
     </row>
     <row xml:id="constant.m-sqrt1-2">
      <entry><constant>M_SQRT1_2</constant></entry>   
      <entry>0.70710678118654752440</entry>
      <entry>1/sqrt(2)</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.m-lnpi">
      <entry><constant>M_LNPI</constant></entry>  
      <entry>1.14472988584940017414</entry>
      <entry>log_e(pi)</entry>
      <entry>PHP 5.2.0</entry>
     </row>
     <row xml:id="constant.m-euler">
      <entry><constant>M_EULER</constant></entry> 
      <entry>0.57721566490153286061</entry>
      <entry>Euler constant</entry>
      <entry>PHP 5.2.0</entry>
     </row>
     <row xml:id="constant.php-round-half-up">
      <entry><constant>PHP_ROUND_HALF_UP</constant></entry> 
      <entry>1</entry>
      <entry>Round halves up</entry>
      <entry>PHP 5.3.0</entry>
     </row>
     <row xml:id="constant.php-round-half-down">
      <entry><constant>PHP_ROUND_HALF_DOWN</constant></entry> 
      <entry>2</entry>
      <entry>Round halves down</entry>
      <entry>PHP 5.3.0</entry>
     </row>
     <row xml:id="constant.php-round-half-even">
      <entry><constant>PHP_ROUND_HALF_EVEN</constant></entry> 
      <entry>3</entry>
      <entry>Round halves to even numbers</entry>
      <entry>PHP 5.3.0</entry>
     </row>
     <row xml:id="constant.php-round-half-odd">
      <entry><constant>PHP_ROUND_HALF_ODD</constant></entry> 
      <entry>4</entry>
      <entry>Round halves to odd numbers</entry>
      <entry>PHP 5.3.0</entry>
     </row>
     <row xml:id="constant.nan">
      <entry><constant>NAN</constant></entry>
      <entry>NAN (as a float)</entry>
      <entry>Not A Number</entry>
      <entry></entry>
     </row>
     <row xml:id="constant.inf">
      <entry><constant>INF</constant></entry>
      <entry>INF (as a float)</entry>
      <entry>The infinite</entry>
      <entry></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </para>
 <para>
  All constants without a labeled PHP version above are available 
  starting with PHP 5.0.0.
 </para>
</appendix>

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