PHP: Magic constants

Magic constants

PHP Manual

Magic constants are keywords that are replaced with information about their own location in the source code: their file and line, and the function, class, trait, namespace, or property hook enclosing them. Despite their name, they are not actual constants: defined() and constant() do not recognize them, and a constant of the same name created with define() does not affect them. They are case-insensitive. When used outside of the relevant context (e.g. __CLASS__ outside of a class), they are replaced with an empty string.

**PHP's magic constants**
Name	Description
`__LINE__`	The line number on which it is written.
`__FILE__`	The full path and filename of the file in which it is written, with symlinks resolved.
`__DIR__`	The directory of the file, equivalent to `dirname(__FILE__)`. It has no trailing slash unless it is the root directory.
`__FUNCTION__`	The name of the function in which it is written, including its namespace (e.g. `Foo\bar`). Inside a method, only the method name. For anonymous functions, a name generated by the engine that includes where the closure was defined (as of PHP 8.4.0; previously `{closure}`).
`__CLASS__`	The name of the class in which it is written, including its namespace (e.g. `Foo\Bar`). Inside a trait, the name of the class using the trait. For anonymous classes, a name generated by the engine. To get the name of the class a method was called on, use `static::class`.
`__TRAIT__`	The trait name, including its namespace (e.g. `Foo\Bar`).
`__METHOD__`	The class and method name of the method in which it is written (e.g. `Foo\Bar::baz`). Inside a trait, the trait name is used instead of the class name. Outside of a method, the same as `__FUNCTION__`.
`__PROPERTY__`	The name of the property, when used inside a property hook. Available as of PHP 8.4.0.
`__NAMESPACE__`	The name of the current namespace.

Example #1 Using magic constants

<?php
namespace App;

function helper()
{
    echo __FUNCTION__, "\n";
    echo __METHOD__, "\n";
}

trait Greets
{
    public function greet()
    {
        echo __CLASS__, "\n";
        echo __TRAIT__, "\n";
        echo __METHOD__, "\n";
        echo __FUNCTION__, "\n";
    }
}

class Greeter
{
    use Greets;
}

helper();
(new Greeter)->greet();
echo __NAMESPACE__, "\n";

The above example will output:

App\helper
App\helper
App\Greeter
App\Greets
App\Greets::greet
greet
App

See Also