Singleton Design Pattern

SingletonPattern.php

<?php

class Counter
{
  
  protected $count = 0;
  
  static private $instance = null;
  
  // protected will ensure that this class only created once
  protected function __construct()
  {
  }
  
  /**
   * Private __clone will prevent cloning of the instance of the "Singleton" object
   */
  protected function __clone()
  {
  }
  
  /**
    * Private __wakeup method to prevent unserializing of the *Singleton*
    * instance.
    */
  private function __wakeup()
  {
  }
  
  public function getCount()
  {
    return $this->count;
  }
  
  public function setCount($count)
  {
    $this->count = $count;
  }
  
  // create an object if not already created
  // returns the current instance of object
  static public function getInstance()
  {
    if(null === static::$instance){
      static::$instance = new static();
    }
    return static::$instance;
  }
}

$ob1 = Counter::getInstance();
$ob1->setCounter(5);
echo Counter::getInstance()->getCount();// will output 5;
Counter::getInstance()->setCount(4);

$ob2 = Counter::getInstance();
echo $ob2->getCount();//will output 4