(new EmptyRule())->satified('abc'); // false
(new EmptyRule())->satified(''); // true
(new EmptyRule())->apply('abc'); // \UnexpectedValueException - 'Subject is not empty'
(new FriendlyRule(new EmptyRule(), 'Not empty!'))->apply('abc'); // \UnexpectedValueException - 'Not empty!'

链式规则

(new ChainedRule(
	new FriendlyRule(
		new NegateRule(new EmptyRule()),
		'Value can not be empty'
	),
	new LengthRule(10),
	new PassiveRule, // it does nothing
	new EmailRule(),
))->apply('abc');

以上代码表明值不能为空，值的长度必须是确切的10个字符，并且值必须是电子邮件。