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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head>  <title>Predefined Constants</title>  <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="math.resources.html">Resource Types</a></div> <div class="next" style="text-align: right; float: right;"><a href="ref.math.html">Math Functions</a></div> <div class="up"><a href="book.math.html">Math</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div> <h1>Predefined Constants</h1> <p class="simpara">The constants below are always available as part of the PHP core.</p> <p class="para">  <table border="5">   <caption><b>Math constants</b></caption>   <colgroup>    <thead valign="middle">     <tr valign="middle">      <th colspan="1">Constant</th>      <th colspan="1">Value</th>      <th colspan="1">Description</th>     </tr>    </thead>    <tbody valign="middle" class="tbody">     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_PI</td>      <td colspan="1" rowspan="1" align="left">3.14159265358979323846</td>      <td colspan="1" rowspan="1" align="left">Pi</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_E</td>      <td colspan="1" rowspan="1" align="left">2.7182818284590452354</td>      <td colspan="1" rowspan="1" align="left">e</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_LOG2E</td>       <td colspan="1" rowspan="1" align="left">1.4426950408889634074</td>      <td colspan="1" rowspan="1" align="left">log_2 e</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_LOG10E</td>      <td colspan="1" rowspan="1" align="left">0.43429448190325182765</td>      <td colspan="1" rowspan="1" align="left">log_10 e</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_LN2</td>         <td colspan="1" rowspan="1" align="left">0.69314718055994530942</td>      <td colspan="1" rowspan="1" align="left">log_e 2</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_LN10</td>        <td colspan="1" rowspan="1" align="left">2.30258509299404568402</td>      <td colspan="1" rowspan="1" align="left">log_e 10</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_PI_2</td>      <td colspan="1" rowspan="1" align="left">1.57079632679489661923</td>      <td colspan="1" rowspan="1" align="left">pi/2</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_PI_4</td>     <td colspan="1" rowspan="1" align="left">0.78539816339744830962</td>      <td colspan="1" rowspan="1" align="left">pi/4</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_1_PI</td>      <td colspan="1" rowspan="1" align="left">0.31830988618379067154</td>      <td colspan="1" rowspan="1" align="left">1/pi</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_2_PI</td>      <td colspan="1" rowspan="1" align="left">0.63661977236758134308</td>      <td colspan="1" rowspan="1" align="left">2/pi</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_SQRTPI</td>          <td colspan="1" rowspan="1" align="left">1.77245385090551602729</td>      <td colspan="1" rowspan="1" align="left">sqrt(pi) [5.2.0]</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_2_SQRTPI</td>        <td colspan="1" rowspan="1" align="left">1.12837916709551257390</td>      <td colspan="1" rowspan="1" align="left">2/sqrt(pi)</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_SQRT2</td>       <td colspan="1" rowspan="1" align="left">1.41421356237309504880</td>      <td colspan="1" rowspan="1" align="left">sqrt(2)</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_SQRT3</td>       <td colspan="1" rowspan="1" align="left">1.73205080756887729352</td>      <td colspan="1" rowspan="1" align="left">sqrt(3) [5.2.0]</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_SQRT1_2</td>         <td colspan="1" rowspan="1" align="left">0.70710678118654752440</td>      <td colspan="1" rowspan="1" align="left">1/sqrt(2)</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_LNPI</td>        <td colspan="1" rowspan="1" align="left">1.14472988584940017414</td>      <td colspan="1" rowspan="1" align="left">log_e(pi) [5.2.0]</td>     </tr>     <tr valign="middle">      <td colspan="1" rowspan="1" align="left">M_EULER</td>       <td colspan="1" rowspan="1" align="left">0.57721566490153286061</td>      <td colspan="1" rowspan="1" align="left">Euler constant [5.2.0]</td>     </tr>    </tbody>   </colgroup>  </table>  Only M_PI is available in PHP versions up to and including PHP 4.0.0.  All other constants are available starting with PHP 4.0.0. Constants  labeled [5.2.0] were added in PHP 5.2.0. </p></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="math.resources.html">Resource Types</a></div> <div class="next" style="text-align: right; float: right;"><a href="ref.math.html">Math Functions</a></div> <div class="up"><a href="book.math.html">Math</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>
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