Singleton Design Pattern

singleton-example.php

<?php 
final class Sample_Plugin {

  private static $instance;
  
  // prevent direct instantiation
  private function __construct() {
  
  }
  
  public static function init(){
    // lets return the instance if we have already
    if (isset( self::$instance)) return self::$instance;
    //at this point, we do not have instance ready, so, let's initialize it, store it and return it.
    self::$instance = new self;
    //....other neccessary stuff and at the end, return the instance
    return self::$instance;
  }
  
  // optionally, it is best practice to prevent cloning and serialization by return exception from __clone and __wakeup

}

// helper function to get a true instance of Sample_Plugin
function sample_plugin() {
  return Sample_Plugin::init();
}

// lets run the plugin
sample_plugin();