// The singleton method
public static function singleton()
{
if (!isset(self::$instance)) {
$c = __CLASS__;
self::$instance = new $c();
}
return self::$instance;
}
// Example method
public function bark()
{
echo 'Woof!';
}
// Prevent users to clone the instance
public function __clone()
{
//trigger_error('Clone is not allowed.', E_USER_ERROR);
echo "throw clone error\n";
}
}
// This would fail because the constructor is private
//$test = new Example;
// This will always retrieve a single instance of the class
$test = Example::singleton();
$test->bark();
// This will issue an E_USER_ERROR.
$test_clone = clone $test;
?>