protected static function getBuiltIn()
	{
		if (self::$built_in === null) {
			self::$built_in = require(dirname(__DIR__) . '/mime.types.php');
		}
		return self::$built_in;
	}
protected static function getBuiltIn()
	{
		if (self::$built_in === null) {
			self::$built_in = require(dirname(__DIR__) . '/mime.types.php');
		}
		return self::$built_in;
	}
protected static function getBuiltIn ( ) { if ( self :: $ built_in === null ) { self :: $ built_in = require ( dirname ( __DIR__ ) . '/mime.types.php' ) ; } return self :: $ built_in ; }
Get the built-in mapping.

@return array The built-in mapping.
Get the built - in mapping .