What is PHP error levels and their numeric values as well as constant?

Error Levels

The following values and constants can be used within the error_reporting() function.

value	constant
1	E_ERROR
2	E_WARNING
4	E_PARSE
8	E_NOTICE
16	E_CORE_ERROR
32	E_CORE_WARNING
64	E_COMPILE_ERROR
128	E_COMPILE_WARNING
256	E_USER_ERROR
512	E_USER_WARNING
1024	E_USER_NOTICE
6143	E_ALL
2048	E_STRICT
4096	E_RECOVERABLE_ERROR

Basic Usage

The following is basic usage of PHP's error reporting (using only one level).

//show nothing
error_reporting(0);

//show everything
error_reporting(E_ALL);

//using php.ini and ini_set()
ini_set('error_reporting', E_ALL);

Advanced Usage

The following accounts for multiple error reporting levels.

//show warnings and errors
error_reporting(E_ERROR | ERROR_WARNING);

//show all types but notices
error_reporting(E_ALL ^ E_NOTICE);