Extending Interfaces

Interface Inheritance

Interfaces can extend other interfaces with extends. The child interface inherits all methods from the parent and can add more.

Example

<?php
interface Readable {
    public function read(): string;
}

interface Writable {
    public function write(string $data): void;
}

// ReadWrite extends both
interface ReadWrite extends Readable, Writable {
    public function seek(int $position): void;
}

class FileStream implements ReadWrite {
    public function read(): string { return "data"; }
    public function write(string $data): void {}
    public function seek(int $position): void {}
}

PHP

Full Editor

Pro Tip

Interface inheritance lets you build layered contracts — start with narrow interfaces and compose them into broader ones.

Related Resources

PHP Reference

Complete tag & property list

PHP How-To Guides

Step-by-step practical guides

PHP Exercises

Practice what you've learned