How to add custom view helpers to Zend Framework 2

You should add them to your module.config.php under view_helpers like this:

'view_manager' => array(
    'template_path_stack' => array(
        'ModuleName' => __DIR__ . '/../view',
    ),
),

'view_helpers' => array(
    'factories' => array(
        'showmessages' => function($sm) {
            $helper = new ModuleName\Helper\MessageShower();
            // do stuff with $sm or the $helper
            return $helper;           
        },
    ),
    'invokables' => array(
        'selectmenu' => 'ModuleName\Helper\SelectMenu',   
        'prettyurl'  => 'ModuleName\Helper\PrettyUrl',
    ),  
),

Here I show two ways of creating the helpers. If all they need to do is to be instantiated, just add their name (including namespace) as invokables. If you need to do stuff with them or the ServiceManager, create them through the factories keyword.