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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>Returns exp(number) - 1, computed in a way that is accurate even when the value of number is close to zero</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="function.exp.html">exp</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.floor.html">floor</a></div> <div class="up"><a href="ref.math.html">Math Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="function.expm1" class="refentry"> <div class="refnamediv"> <h1 class="refname">expm1</h1> <p class="verinfo">(PHP 4 >= 4.0.7, PHP 5)</p><p class="refpurpose"><span class="refname">expm1</span> — <span class="dc-title"> Returns exp(number) - 1, computed in a way that is accurate even when the value of number is close to zero </span></p> </div> <div class="refsect1 description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">float</span> <span class="methodname"><b><b>expm1</b></b></span> ( <span class="methodparam"><span class="type">float</span> <tt class="parameter">$arg</tt></span> )</div> <div class="warning"><b class="warning">Warning</b><p class="simpara">This function is<em class="emphasis">EXPERIMENTAL</em>. The behaviour of this function, its name, andsurrounding documentation may change without notice in a future release of PHP.This function should be used at your own risk.</p></div> <p class="para"> <b>expm1()</b> returns the equivalent to 'exp(<i><tt class="parameter">arg</tt></i>) - 1' computed in a way that is accurate even if the value of <i><tt class="parameter">arg</tt></i> is near zero, a case where 'exp (<i><tt class="parameter">arg</tt></i>) - 1' would be inaccurate due to subtraction of two numbers that are nearly equal. </p> </div> <div class="refsect1 parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <span class="term"><i><tt class="parameter">arg</tt></i></span> <dd> <p class="para"> The argument to process </p> </dd> </dt> </dl> </p> </div> <div class="refsect1 returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> 'e' to the power of <i><tt class="parameter">arg</tt></i> minus one </p> </div> <div class="refsect1 changelog"> <h3 class="title">ChangeLog</h3> <p class="para"> <table class="informaltable"> <colgroup> <thead valign="middle"> <tr valign="middle"> <th colspan="1">Version</th> <th colspan="1">Description</th> </tr> </thead> <tbody valign="middle" class="tbody"> <tr valign="middle"> <td colspan="1" rowspan="1" align="left">5.3.0</td> <td colspan="1" rowspan="1" align="left"> This function is now available on all platforms </td> </tr> </tbody> </colgroup> </table> </p> </div> <div class="refsect1 seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"><a href="function.log1p.html" class="function" rel="rdfs-seeAlso">log1p()</a></li> <li class="member"><a href="function.exp.html" class="function" rel="rdfs-seeAlso">exp()</a></li> </ul> </p> </div></div><hr /><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.exp.html">exp</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.floor.html">floor</a></div> <div class="up"><a href="ref.math.html">Math Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div></body></html>⌨️ 快捷键说明
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