改变方法可见性

trait HelloWorld {
    public function sayHello() {
        echo 'Hello World!';
    }
}

// Change visibility of sayHello
class MyClass1 {
    use HelloWorld { sayHello as protected; }
}

// Alias method with changed visibility
// sayHello visibility not changed
class MyClass2 {
    use HelloWorld { sayHello as private myPrivateHello; }
}

运行此示例：

(new MyClass1())->sayHello();
// Fatal error: Uncaught Error: Call to protected method MyClass1::sayHello()

(new MyClass2())->myPrivateHello();
// Fatal error: Uncaught Error: Call to private method MyClass2::myPrivateHello()

(new MyClass2())->sayHello();
// Hello World!

因此请注意，在 MyClass2 的最后一个示例中，trait HelloWorld 的原始无法使用的方法保持原样可访问。