# The SplObserver interface

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

## Introduction

The SplObserver interface is used alongside SplSubject to implement the Observer Design Pattern.

## Interface synopsis

interface SplObserver {
/* Methods */
public update(SplSubject `$subject`): void
}

## Table of Contents

- SplObserver::update — Receive update from subject

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