Magic constants

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:

PHP's magic constants

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.