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<title>Returns exp(number) - 1, computed in a way that is accurate even
when the value of number is close to zero</title>
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<h1 class="refname">expm1</h1>
<p class="verinfo">(PHP 4 >= 4.1.0, PHP 5, PHP 7)</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" id="refsect1-function.expm1-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">float</span> <span class="methodname"><strong>expm1</strong></span>
( <span class="methodparam"><span class="type">float</span> <code class="parameter">$arg</code></span>
)</div>
<p class="para rdfs-comment">
<span class="function"><strong>expm1()</strong></span> returns the equivalent to
'exp(<code class="parameter">arg</code>) - 1' computed in a way that is
accurate even if the value of <code class="parameter">arg</code> is near zero,
a case where 'exp (<code class="parameter">arg</code>) - 1' would be
inaccurate due to subtraction of two numbers that are nearly equal.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.expm1-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">arg</code></dt>
<dd>
<p class="para">
The argument to process
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.expm1-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
'e' to the power of <code class="parameter">arg</code> minus one
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.expm1-changelog">
<h3 class="title">Changelog</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>5.3.0</td>
<td>
This function is now available on all platforms
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.expm1-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><span class="function"><a href="function.log1p.html" class="function" rel="rdfs-seeAlso">log1p()</a> - Returns log(1 + number), computed in a way that is accurate even when
the value of number is close to zero</span></li>
<li class="member"><span class="function"><a href="function.exp.html" class="function" rel="rdfs-seeAlso">exp()</a> - Calculates the exponent of e</span></li>
</ul>
</p>
</div>
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