Magic constants are the pre-defined constants accessible to PHP scripts. Magic constant starts and ends with a double underscore (__).

PHP Magic Constant:

• __FUNCTION__ The function name
• __METHOD__ The class method name
• __CLASS__ The class name
• __LINE__ The current line number of the file
• __FILE__ The full path and filename of the file
• PHP_VERSION The PHP version
• PHP_INT_MAX The PHP integer value limit