PHP常见带有下划线的常量

1、__PHP_Incomplete_Class

<?php
  echo __PHP_Incomplete_Class::class;
?>

__PHP_Incomplete_Class

2、__CLASS__

<?php
  echo __CLASS__;
?>

3、__DIR__

<?php
  echo __DIR__;
?>

E:\phpworkspace\PHP

4、__FILE__

<?php
  echo __FILE__;
?>

E:\phpworkspace\PHP

5、__FUNCTION__

<?php
  echo __FUNCTION__;
?>

E:\phpworkspace\PHP

6、__LINE__

<?php
  echo __LINE__;
?>

2

7、__METHOD__

<?php
  echo __METHOD__;
?>

8、__NAMESPACE__

<?php
  echo __NAMESPACE__;
?>