How do you bind an interface to a specific concrete implementation within a service container, and why is this a common and valuable pattern?

Binding an interface to a concrete implementation tells the service container which specific class should be used whenever a class requests that interface as a dependency, which is valuable because it lets the rest of your application depend only on the interface, remaining completely unaware of the specific implementation being used, meaning you can swap the underlying implementation, such as switching from a file based cache to a Redis based cache, by changing just one line of container configuration.

$container->bind(CacheInterface::class, RedisCache::class);

class ReportService {
    public function __construct(private CacheInterface $cache) {}
}