Interface Constants
Interfaces can define constants that implementing classes inherit. They cannot be overridden by implementing classes (as of PHP 8.1, they can be declared final).
PHP
Intermediate
4 min read
Interface Constants
Example
<?php
interface StatusCodes {
const OK = 200;
const NOT_FOUND = 404;
const SERVER_ERROR = 500;
const CREATED = 201;
const NO_CONTENT = 204;
}
class ApiResponse implements StatusCodes {
public function ok(array $data): array {
return ["status" => self::OK, "data" => $data];
}
public function notFound(string $msg): array {
return ["status" => self::NOT_FOUND, "error" => $msg];
}
}
echo ApiResponse::OK; // 200
echo StatusCodes::NOT_FOUND; // 404 Pro Tip
Group related constants in interfaces to create named constant sets — all implementing classes get them automatically.