Common pre-defined constants for PHP

__FILE__: Current file name

__LINE__: currently in the row

__FUNCTION__: Name of current function

__CLASS__: Current class name

__method__: Current method name

Php_os: Operating system that executes the script

php_version:php Server version number

True: Boolean value True

False: Boolean value false

Null: null value

Directory_separator: Operating System directory Separator

E_error: Error, inverted PHP script stops running

E_warning: Warning, script not stopped

E_notice: Non-critical error, such as script not initialized

E_parse: Parsing error, reported by parser

M_pi:pi value

Common pre-defined constants for PHP