(PHP 5 >= 5.1.0, PHP 7, PHP 8)
The SplObserver interface is used alongside SplSubject to implement the Observer Design Pattern.
Beware, you have written :
if($key){
unset($this->observers[$key]);
}
When this should be :
if(false !== $key){
unset($this->observers[$key]);
}
If the observer you want to delete is the first in your array, you will never delete it because the key would equal 0 and 0 == false as you know.
<?php
/**
* Subject,that who makes news
*/
class Newspaper implements \SplSubject{
private $name;
private $observers = array();
private $content;
public function __construct($name) {
$this->name = $name;
}
//add observer
public function attach(\SplObserver $observer) {
$this->observers[] = $observer;
}
//remove observer
public function detach(\SplObserver $observer) {
$key = array_search($observer,$this->observers, true);
if($key){
unset($this->observers[$key]);
}
}
//set breakouts news
public function breakOutNews($content) {
$this->content = $content;
$this->notify();
}
public function getContent() {
return $this->content." ({$this->name})";
}
//notify observers(or some of them)
public function notify() {
foreach ($this->observers as $value) {
$value->update($this);
}
}
}
/**
* Observer,that who recieves news
*/
class Reader implements SplObserver{
private $name;
public function __construct($name) {
$this->name = $name;
}
public function update(\SplSubject $subject) {
echo $this->name.' is reading breakout news <b>'.$subject->getContent().'</b><br>';
}
}
$newspaper = new Newspaper('Newyork Times');
$allen = new Reader('Allen');
$jim = new Reader('Jim');
$linda = new Reader('Linda');
//add reader
$newspaper->attach($allen);
$newspaper->attach($jim);
$newspaper->attach($linda);
//remove reader
$newspaper->detach($linda);
//set break outs
$newspaper->breakOutNews('USA break down!');
//=====output======
//Allen is reading breakout news USA break down! (Newyork Times)
//Jim is reading breakout news USA break down! (Newyork Times)