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<?php
/**
* @package ActiveRecord
*/
namespace ActiveRecord;
/**
* This implementation of the singleton pattern does not conform to the strong definition
* given by the "Gang of Four." The __construct() method has not be privatized so that
* a singleton pattern is capable of being achieved; however, multiple instantiations are also
* possible. This allows the user more freedom with this pattern.
*
* @package ActiveRecord
*/
abstract class Singleton
{
/**
* Array of cached singleton objects.
*
* @var array
*/
private static $instances = array();
/**
* Static method for instantiating a singleton object.
*
* @return object
*/
final public static function instance()
{
$class_name = get_called_class();
if (!isset(self::$instances[$class_name]))
self::$instances[$class_name] = new $class_name;
return self::$instances[$class_name];
}
/**
* Singleton objects should not be cloned.
*
* @return void
*/
final private function __clone() {}
/**
* Similar to a get_called_class() for a child class to invoke.
*
* @return string
*/
final protected function get_called_class()
{
$backtrace = debug_backtrace();
return get_class($backtrace[2]['object']);
}
}
?>
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