public function register($key, $callable)
	{
		if (!$this->has($key) && is_callable($callable))
		{
			self::$registry[$key] = $callable;
			return true;
		}

		return false;
	}
public function register($key, $callable)
	{
		if (!$this->has($key) && is_callable($callable))
		{
			self::$registry[$key] = $callable;
			return true;
		}

		return false;
	}
public function register ( $ key , $ callable ) { if ( ! $ this -> has ( $ key ) && is_callable ( $ callable ) ) { self :: $ registry [ $ key ] = $ callable ; return true ; } return false ; }
Registers a function to be called with a specific key

@param   string   $key       The name of the key
@param   array    $callable  Function or method
@return  boolean  True if the function is callable
Registers a function to be called with a specific key