Source of: /manual/en/function.constant.php
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<div id="function.constant" class="refentry">
<div class="refnamediv">
<h1 class="refname">constant</h1>
<p class="verinfo">(PHP 4 >= 4.0.4, PHP 5)</p><p class="refpurpose"><span class="refname">constant</span> — <span class="dc-title">Returns the value of a constant</span></p>
</div>
<a name="function.constant.description"></a><div class="refsect1 description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type"><a href="language.pseudo-types.php#language.types.mixed" class="type mixed">mixed</a></span> <span class="methodname"><b>constant</b></span>
( <span class="methodparam"><span class="type">string</span> <tt class="parameter">$name</tt></span>
)</div>
<p class="simpara">
Return the value of the constant indicated by
<i><tt class="parameter">name</tt></i>
.
</p>
<p class="simpara">
<b>constant()</b> is useful if you need to retrieve
the value of a constant, but do not know its name. I.e. it is
stored in a variable or returned by a function.
</p>
<p class="simpara">
This function works also with <a href="language.oop5.constants.php" class="link">class constants</a>.
</p>
</div>
<a name="function.constant.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">name</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
The constant name.
</p>
</dd>
</dl>
<p>
</p>
</div>
<a name="function.constant.returnvalues"></a><div class="refsect1 returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the value of the constant, or <b><tt class="constant">NULL</tt></b> if the constant is not
defined.
</p>
</div>
<a name="function.constant.examples"></a><div class="refsect1 examples">
<h3 class="title">Examples</h3>
<p class="para">
</p><div class="example">
<p><b>Example #1 <b>constant()</b> example</b></p>
<div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />define</span><span style="color: #007700">(</span><span style="color: #DD0000">"MAXSIZE"</span><span style="color: #007700">, </span><span style="color: #0000BB">100</span><span style="color: #007700">);<br /><br />echo </span><span style="color: #0000BB">MAXSIZE</span><span style="color: #007700">;<br />echo </span><span style="color: #0000BB">constant</span><span style="color: #007700">(</span><span style="color: #DD0000">"MAXSIZE"</span><span style="color: #007700">); </span><span style="color: #FF8000">// same thing as the previous line<br /><br /><br /></span><span style="color: #007700">interface </span><span style="color: #0000BB">bar </span><span style="color: #007700">{<br /> const </span><span style="color: #0000BB">test </span><span style="color: #007700">= </span><span style="color: #DD0000">'foobar!'</span><span style="color: #007700">;<br />}<br /><br />class </span><span style="color: #0000BB">foo </span><span style="color: #007700">{<br /> const </span><span style="color: #0000BB">test </span><span style="color: #007700">= </span><span style="color: #DD0000">'foobar!'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">$const </span><span style="color: #007700">= </span><span style="color: #DD0000">'test'</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">constant</span><span style="color: #007700">(</span><span style="color: #DD0000">'bar::'</span><span style="color: #007700">. </span><span style="color: #0000BB">$const</span><span style="color: #007700">)); </span><span style="color: #FF8000">// string(7) "foobar!"<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">constant</span><span style="color: #007700">(</span><span style="color: #DD0000">'foo::'</span><span style="color: #007700">. </span><span style="color: #0000BB">$const</span><span style="color: #007700">)); </span><span style="color: #FF8000">// string(7) "foobar!"<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div><p>
</p>
</div>
<a name="function.constant.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.define.php" class="function" rel="rdfs-seeAlso">define()</a> - Defines a named constant</li>
<li class="member"><a href="function.defined.php" class="function" rel="rdfs-seeAlso">defined()</a> - Checks whether a given named constant exists</li>
<li class="member">The section on <a href="language.constants.php" class="link">Constants</a></li>
</ul><p>
</p>
</div>
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