singleton.php

<?php

class DebuggerEcho implements Debugger 
{
  
  protected function __construct() {}
  private function __clone() {}
  
  public static function getInstance() 
  {
    if (null == self::$instance) 
    {
      self::$instance = new self();
    }
      return self::$instance;
  }
  
  public function debug($message) 
  {
    print $message . "\n";
  }
}

// AKA multition
class DebuggerLog implements Debugger
{
    protected $logfile = null;
    private static $instances = array();
    public static function getInstance($logfile)
    {
        if (!isset(self::$instances[$logfile])) {
            self::$instances[$logfile] = new self($logfile);
        }
        return self::$instances[$logfile];
    }
    protected function __construct($logfile)
    {
        $this->logfile = $logfile;
    }
    private function __clone()
    {
    }
    public function debug($message)
    {
        error_log($message . "\n", 3, $this->logfile);
    }
}

// usage
$debugger1 = DebuggerLog::getInstance('./debugger1.log');
$debugger1->debug('Lorem ipsum dolor sit amet.');
$debugger2 = DebuggerLog::getInstance('./debugger2.log');
$debugger2->debug('Proin fringilla bibendum sagittis.');
$debugger3 = DebuggerLog::getInstance('./debugger1.log');
$debugger3->debug('Mauris vitae augue dolor.');