PHP Magic Constants

PHP Predefined Constants

PHP has nine predefined constants that change value depending on where they are used, and therefor they are called "magic constants".

These magic constants are written with a double underscore at the start and the end, except for the ClassName::class constant.

Here are the magic constants, with descriptions and examples:

Constant	Description
__CLASS__	If used inside a class, the class name is returned.	Try it »
__DIR__	The directory of the file.	Try it »
__FILE__	The file name including the full path.	Try it »
__FUNCTION__	If inside a function, the function name is returned.	Try it »
__LINE__	The current line number.	Try it »
__METHOD__	If used inside a function that belongs to a class, both class and function name is returned.	Try it »
__NAMESPACE__	If used inside a namespace, the name of the namespace is returned.	Try it »
__TRAIT__	If used inside a trait, the trait name is returned.	Try it »
ClassName::class	Returns the name of the specified class and the name of the namespace, if any.	Try it »

Note:

The magic constants are case-insensitive, meaning __LINE__ returns the same as __line__.