added interface documentation

drafts/records.md

@@ -289,6 +289,46 @@ record User(string $name, string $emailAddress) {
 }
 ```
 
+### Implementing Interfaces
+
+A **record** can implement interfaces, but it cannot extend other records or classes, but may use traits:
+
+```php
+interface Vehicle {}
+
+interface Car extends Vehicle {
+  public function drive(): void;
+}
+
+interface SpaceShip extends Vehicle {
+  public function launch(): void;
+}
+
+record FancyCar(string $model) implements Car {
+  public function drive(): void {
+    echo "Driving a Fancy Car {$this->model}";
+  }
+}
+
+record SpaceCar(string $model) implements Car, SpaceShip {
+  public function drive(): void {
+    echo "Driving a Space Car {$this->model}";
+  }
+
+  public function launch(): void {
+    echo "Launching a Space Car {$this->model}";
+  }
+}
+
+record Submarine(string $model) implements Vehicle {
+  use Submersible;
+}
+
+record TowTruct(string $model, private Car $towing) implements Car {
+  use Towable;
+}
+```
+
 ### Mental models and how it works
 
 From the perspective of a developer, declaring a record declares an object with the same name.

published/records.ptxt

@@ -245,6 +245,46 @@ record User(string $name, string $emailAddress) {
 }
 </code>
 
+==== Implementing Interfaces ====
+
+A **record** can implement interfaces, but it cannot extend other records or classes, but may use traits:
+
+<code php>
+interface Vehicle {}
+
+interface Car extends Vehicle {
+  public function drive(): void;
+}
+
+interface SpaceShip extends Vehicle {
+  public function launch(): void;
+}
+
+record FancyCar(string $model) implements Car {
+  public function drive(): void {
+    echo "Driving a Fancy Car {$this->model}";
+  }
+}
+
+record SpaceCar(string $model) implements Car, SpaceShip {
+  public function drive(): void {
+    echo "Driving a Space Car {$this->model}";
+  }
+
+  public function launch(): void {
+    echo "Launching a Space Car {$this->model}";
+  }
+}
+
+record Submarine(string $model) implements Vehicle {
+  use Submersible;
+}
+
+record TowTruct(string $model, private Car $towing) implements Car {
+  use Towable;
+}
+</code>
+
 ==== Mental models and how it works ====
 
 From the perspective of a developer, declaring a record declares an object with the same name. The developer can consider the record function (the inline constructor) as a factory function that creates a new object or retrieves an existing object from an array.