How to add custom view helpers to Zend Framework 2

Answer

add view helpers to 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 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 we need to do stuff with them or the ServiceManager, create them through the factories keyword.