php Magical Constants(_LINE_,_FILE_,_FUNCTION-,_CLASS_ and _METHOD_)

PHP Constants definition:

• A constant is a name or an identifier for a simple value.
• A constant value cannnot change during the execution of he script.
• By default a constant is case-sensitive.
• By convention, constant identifiers are always uppercase.
• A constant name statrs with a letter or underscore, followed by any number of letters, numbers, or underscores.
• To define a constant, use define() function and retrieve the value of a constant.
• The function constant() is used to read a constant's value.



Syntax:

Result:

  Welcome

Pre-defined constants

PHP provides a large number of predefined constants to any script which it runs.

There are Basically five magical constants that change depending on where they are used.

Name	Description
__LINE__	Represents current line number where it is used.
__FILE__	Represents full path and file name of the file. If it is used inside an include, name of included file is returned.
__FUNCTION__	Represents the function name where it is used. If it is used outside of any function, then it will return blank.
__CLASS__	Represents the class name where it is used. If it is used outside of any function, then it will return blank.
__METHOD__	Represents the name of the class method where it is used. The method name is returned as it was declared.

_LINE_

The current line number of the file where it is used.

Example:_LINE_

Result:

The Line number : 3




Example:_FILE_

Represents full path and file name of the file. If it is used inside an include, name of included file is returned.

Result:

Your file name :D:\SQLBD\htdocs\php\index.php




Example:_FUNCTION_

_FUNCTION_ Represents the function name where it is used. If it is used outside of any function, then it will return blank.
_METHOD_Represents the class name where it is used. If it is used outside of any function, then it will return blank.
_CLASS_Represents the name of the class method where it is used. The method name is returned as it was declared.

Result:

  Function of demo class : test
  Method of demo class : demo::testme
  Class : demo