Hi manjunath,
Magic constants, as they are called, are not acutally constants but effectively behave like constants and are pre-defined. Magic constants use the same naming convention as PHP constants.
There are 7 magic constants that change depending on where they are used. They are listed below.
name description
__LINE__ The current line number of the file.
__FILE__ The full path and filename of the file. If used inside an include, the name of the included file is returned. Since PHP 4.0.2, __FILE__ always contains an absolute path with symlinks resolved whereas in older versions it contained relative path under some circumstances.
__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. (Added in PHP 5.3.0.)
__FUNCTION__ The function name. (Added in PHP 4.3.0) As of PHP 5 this constant returns the function name as it was declared (case-sensitive). In PHP 4 its value is always lowercased.
__CLASS__ The class name. (Added in PHP 4.3.0) As of PHP 5 this constant returns the class name as it was declared (case-sensitive). In PHP 4 its value is always lowercased.
__METHOD__ The class method name. (Added in PHP 5.0.0) The method name is returned as it was declared (case-sensitive).
__NAMESPACE__ The name of the current namespace (case-sensitive). This constant is defined in compile-time (Added in PHP 5.3.0).
Mar 17, 2010
