src/Composer/Util/ErrorHandler.php
public static function register(IOInterface $io = null)
    {
        set_error_handler(array(__CLASS__, 'handle'));
        error_reporting(E_ALL | E_STRICT);
        self::$io = $io;
    }
public static function register(IOInterface $io = null)
    {
        set_error_handler(array(__CLASS__, 'handle'));
        error_reporting(E_ALL | E_STRICT);
        self::$io = $io;
    }
Register error handler.

@param IOInterface|null $io