Singleton Classes

AbstractSingleton.php

<?php

abstract class AbstractSingleton implements SingletonInterface
{
    final public static function getInstance()
    {
      static $instance;
      return $instance = $instance ?: new \static();
    }
    final private function __construct() {}
    final private function __clone() {}
    final private function __sleep() {}
    final private function __wakeup() {}
}

AbstractSingletonTrait.php

<?php

abstract class AbstractSingleton implements SingletonInterface
{
    use SingletonTrait;
}

SingletonInterface.php

<?php 

interface SingletonInterface {
    final public static function getInstance();
}

SingletonTrait.php

<?php

trait SingletonTrait {

  final public static function getInstance(){
    static $instance;
    return $instance = $instance ?: new \static();
  }
  final private function __construct() {}
  final private function __clone() {}
  final private function __sleep() {}
  final private function __wakeup() {}
}

usages.php

<?php

// usages 
class Singleton implements SingletonInterface{
  use SingletonTrait;

}
$instance = Singleton::getInstance();

class Singleton extends AbstractSingleton {

}
$instance = Singleton::getInstance();

class Singleton extends AbstractSingletonTrait {

}
$instance = Singleton::getInstance();