3v4l.org

run code in 300+ PHP versions simultaneously
<?php class A { private static self $singleton; public function __construct() { if(!isset(self::$singleton)) { self::$singleton = $this; } return self::$singleton; } } $a = new A; $b = new A; $c = new A; var_dump($a); var_dump($b); var_dump($c);

preferences:
49.66 ms | 404 KiB | 5 Q