**一.Stringable接口** ``` interface Stringable { public function __toString(): string; } ```   **二.類顯示實現Stringable接口** ``` class Foo implements Stringable{ public function __toString(){ return 'FooBar'; } } $foo = new Foo(); var_dump($foo instanceof Stringable); ```   **三.類隱式實現Stringable接口** ``` class Foo { public function __toString(){ return 'FooBar'; } } $foo = new Foo(); var_dump($foo instanceof Stringable); ```   **四.Stringable類型約束實例** #獲取類命名空間和類名大寫字串 ``` namespace php8; class Person{ public function __toString(){ return self::class; } } function mysafe(\Stringable $obj){ echo strtoupper($obj); } mysafe(new Person); ```   **配套的PHP8新特性詳解視頻教程，請查看以下專輯** 鏈接：[https://www.ixigua.com/6937490165329822219](https://www.ixigua.com/6937490165329822219)