SplObserver¶
SplObserver is an SPL interface that represents the observer role in the Observer design pattern. Classes implementing SplObserver must define the update(SplSubject $subject) method, which is called whenever the observed subject notifies its observers of a state change.
SplObserver is used together with SplSubject: the subject maintains a list of observers and calls their update() method when its internal state changes.
<?php
class Logger implements SplObserver {
public function update(SplSubject $subject): void {
echo 'State changed: ' . $subject->getState() . PHP_EOL;
}
}
?>
See also Observer pattern.
Related : Standard PHP Library (SPL), SplSubject, Observer Design Pattern, Interface, Observer Pattern, PHP Native Interfaces
Added in PHP 5.1
