There are a few magical constants that change depending on
where they are used. For example, the value of
__LINE__ depends on the line that it's
used on in a 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:
| Name | Description |
|---|---|
__LINE__ |
The current line number of the file. |
__FILE__ |
The full path and filename of the file with symlinks resolved. If used inside an include, the name of the included file is returned. |
__DIR__ |
The directory of the file. If used inside an include,
the directory of the included file is returned. This is equivalent
to dirname(__FILE__). This directory name
does not have a trailing slash unless it is the root directory.
|
__FUNCTION__ |
The function name, or {closure} for anonymous functions.
|
__CLASS__ |
The class name. The class name includes the namespace
it was declared in (e.g. Foo\Bar).
When used inside a trait method,
__CLASS__ is the name of the class the trait
is used in.
|
__TRAIT__ |
The trait name. The trait name includes the namespace
it was declared in (e.g. Foo\Bar).
|
__METHOD__ |
The class method name. |
__PROPERTY__ |
Only valid inside a property hook. It is equal to the name of the property. |
__NAMESPACE__ |
The name of the current namespace. |
ClassName::class |
The fully qualified class name. |
<?php
namespace My\App {
class Api {
public static fetch() {
print __FUNCTION__ . "\n"; // outputs fetch
print __METHOD__ . "\n"; // outputs My\App\Api::fetch
}
}
Api::fetch();
}
namespace {
My\App\Api::fetch();
}
?>
__METHOD__ outputs a fully qualified method name; __FUNCTION__ when used in a method, outputs just the method name.Note that __CLASS__ and __METHOD__ both reference the class the code is written in, not whatever the object class is. E.g. if you have an object of class B inheriting from class A, any usage of __CLASS__ in class A is going to give "A".If PHP is run inside a web server request there is an important difference between the __DIR__ constant and $_SERVER['DOCUMENT_ROOT'].
Where __DIR__ of a PHP script contained within a sub-folder will include the complete server path $_SERVER['DOCUMENT_ROOT'] will contain a server path up to the _root_ of the application. This can be helpful when for instance an auto-loader is defined in an include file sitting inside a sub-folder and where the classes are located in another folder at the root of the application.