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</div><hr /><div id="language.constants.predefined" class="sect1">
<h2 class="title">Magic constants</h2>
<p class="simpara">
PHP provides a large number of <a href="reserved.constants.html" class="link">predefined constants</a> to any script
which it runs. Many of these constants, however, are created by
various extensions, and will only be present when those extensions
are available, either via dynamic loading or because they have
been compiled in.
</p>
<p class="para">
There are nine magical constants that change depending on
where they are used. For example, the value of
<strong><code>__LINE__</code></strong> depends on the line that it's
used on in your script. All these "magical" constants are resolved
at compile time, unlike regular constants, which are resolved at runtime.
These special constants are case-insensitive and are as follows:
</p>
<p class="para">
<table class="doctable table">
<caption><strong>A few "magical" PHP constants</strong></caption>
<thead>
<tr>
<th>Name</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr id="constant.line">
<td><strong><code>__LINE__</code></strong></td>
<td>
The current line number of the file.
</td>
</tr>
<tr id="constant.file">
<td><strong><code>__FILE__</code></strong></td>
<td>
The full path and filename of the file with symlinks resolved. If used inside an include,
the name of the included file is returned.
</td>
</tr>
<tr id="constant.dir">
<td><strong><code>__DIR__</code></strong></td>
<td>
The directory of the file. If used inside an include,
the directory of the included file is returned. This is equivalent
to <em>dirname(__FILE__)</em>. This directory name
does not have a trailing slash unless it is the root directory.
</td>
</tr>
<tr id="constant.function">
<td><strong><code>__FUNCTION__</code></strong></td>
<td>
The function name.
</td>
</tr>
<tr id="constant.class">
<td><strong><code>__CLASS__</code></strong></td>
<td>
The class name. The class name includes the namespace
it was declared in (e.g. <em>Foo\Bar</em>).
Note that as of PHP 5.4 __CLASS__ works also in traits. When used
in a trait method, __CLASS__ is the name of the class the trait
is used in.
</td>
</tr>
<tr id="constant.trait">
<td><strong><code>__TRAIT__</code></strong></td>
<td>
The trait name. The trait name includes the namespace
it was declared in (e.g. <em>Foo\Bar</em>).
</td>
</tr>
<tr id="constant.method">
<td><strong><code>__METHOD__</code></strong></td>
<td>
The class method name.
</td>
</tr>
<tr id="constant.namespace">
<td><strong><code>__NAMESPACE__</code></strong></td>
<td>
The name of the current namespace.
</td>
</tr>
<tr id="constant.coloncolonclass">
<td><strong><code>ClassName::class</code></strong></td>
<td>
The fully qualified class name. See also
<a href="language.oop5.basic.html#language.oop5.basic.class.class" class="link">::class</a>.
</td>
</tr>
</tbody>
</table>
</p>
<p class="para">
See also
<span class="function"><a href="function.get-class.html" class="function">get_class()</a></span>,
<span class="function"><a href="function.get-object-vars.html" class="function">get_object_vars()</a></span>,
<span class="function"><a href="function.file-exists.html" class="function">file_exists()</a></span> and
<span class="function"><a href="function.function-exists.html" class="function">function_exists()</a></span>.
</p>
<div class="sect2" id="language.constants.predefined.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>5.5.0</td>
<td>
Added <strong><code>::class</code></strong> magic constant
</td>
</tr>
<tr>
<td>5.4.0</td>
<td>
Added <strong><code>__TRAIT__</code></strong> constant
</td>
</tr>
<tr>
<td>5.3.0</td>
<td>
Added <strong><code>__DIR__</code></strong> and <strong><code>__NAMESPACE__</code></strong> constants
</td>
</tr>
<tr>
<td>5.0.0</td>
<td>
Added <strong><code>__METHOD__</code></strong> constant
</td>
</tr>
<tr>
<td>5.0.0</td>
<td>
Before this version values of some magic constants were always lowercased.
All of them are case-sensitive now (contain names as they were declared).
</td>
</tr>
<tr>
<td>4.3.0</td>
<td>
Added <strong><code>__FUNCTION__</code></strong> and <strong><code>__CLASS__</code></strong> constants
</td>
</tr>
<tr>
<td>4.0.2</td>
<td>
<strong><code>__FILE__</code></strong> always contains an absolute path with symlinks
resolved whereas in older versions it contained relative path
under some circumstances
</td>
</tr>
</tbody>
</table>
</p>
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