Source of: /manual/en/function.expm1.php
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<div id="function.expm1" class="refentry">
<div class="refnamediv">
<h1 class="refname">expm1</h1>
<p class="verinfo">(PHP 4 >= 4.1.0, 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>
<a name="function.expm1.description"></a><div class="refsect1 description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">float</span> <span class="methodname"><b>expm1</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, and
surrounding 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>
<a name="function.expm1.parameters"></a><div class="refsect1 parameters">
<h3 class="title">Parameters</h3>
<p class="para">
</p><dl>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">arg</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
The argument to process
</p>
</dd>
</dl>
<p>
</p>
</div>
<a name="function.expm1.returnvalues"></a><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>
<a name="function.expm1.changelog"></a><div class="refsect1 changelog">
<h3 class="title">Changelog</h3>
<p class="para">
</p><table class="doctable informaltable">
<thead valign="middle">
<tr valign="middle">
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody valign="middle" class="tbody">
<tr valign="middle">
<td align="left">5.3.0</td>
<td align="left">
This function is now available on all platforms
</td>
</tr>
</tbody>
</table>
<p>
</p>
</div>
<a name="function.expm1.seealso"></a><div class="refsect1 seealso">
<h3 class="title">See Also</h3>
<p class="para">
</p><ul class="simplelist">
<li class="member"><a href="function.log1p.php" 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</li>
<li class="member"><a href="function.exp.php" class="function" rel="rdfs-seeAlso">exp()</a> - Calculates the exponent of e</li>
</ul><p>
</p>
</div>
</div><?php manual_footer(); ?>
