Constants commonly used in PHP

There are seven magic constants whose values change as they change position in the Code. For example, the value of __line__ depends on the row it is in the script to Determine. These special constants are case-insensitive, as Follows:

name	Description
__line__	The current line number in the File.
__file__	The full path and file name of the File. If used in the included file, returns the file name that is Included. From PHP 4.0.2,__file__ always contains an absolute path (if it is a symbolic connection, the resolved absolute path), and the previous version sometimes contains a relative path.
__dir__	The directory where the file Resides. If used in the included file, returns the directory where the included files are Located. It is equivalent to dirname (__file__). Unless it is a root directory, the name in the directory does not include the trailing Slash. (new in PHP 5.3.0) =
__function__	The name of the function (PHP 4.3.0 new addition). From PHP 5 This constant returns the name (case-sensitive) when the function is Defined. In PHP 4, This value is always in lowercase letters.
__class__	The name of the class (PHP 4.3.0 new addition). From PHP 5 This constant returns the name of the class when it is defined (case-sensitive). In PHP 4, This value is always in lowercase letters.
__method__	The method name of the class (PHP 5.0.0 new addition). Returns the name of the method when it is defined (case-sensitive).
__namespace__	The name of the current namespace (case sensitive). This constant is defined at compile time (PHP 5.3.0 new)

Constants commonly used in PHP