3v4l.org

run code in 300+ PHP versions simultaneously
<?php interface Counter { /** @return self */ public function count(); /** @return int */ public function getCount(); } class EchoingCounter implements Counter { private $counter; public function __construct(Counter $counter) { $this->counter = $counter; } public function count() { echo __METHOD__ . "\n"; $this->counter->count(); return $this; } public function getCount() { echo __METHOD__ . "\n"; return $this->counter->getCount(); } } class ImmutableCounter implements Counter { private $count; public function __construct($count = 0) { $this->count = (int) $count; } public function count() { return new ImmutableCounter($this->count + 1); } public function getCount() { return $this->count; } } $counter = new EchoingCounter(new ImmutableCounter()); $counter = $counter->count()->count()->count()->count(); echo $counter->getCount();
Output for 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
EchoingCounter::count EchoingCounter::count EchoingCounter::count EchoingCounter::count EchoingCounter::getCount 0

preferences:
255.73 ms | 404 KiB | 411 Q