New hooks

[cupcakes]

I've followed this guide for how to create a new hook: http://www.prestashop.com/forums/topic/2182[spam-filter]create-custom-and-new-hook-in-ps-15/

 

First I had an issue with transplanting a module to the new hook - I tried adding the code mentioned in the guide above to the modules php, but still no luck.

 

Then another issue appeared a few days later on the website, where this appears: 
 

Notice: Undefined index: HOOK_displayHeadermenu in /storage/content/21/104221/website.com/public_html/cache/smarty/compile/26/7c/16/267c169b968f1f3a3b5d651baaf0b52c9b543f4e.file.header.tpl.php on line 167 Notice: Trying to get property of non-object in /storage/content/21/104221/website.com/public_html/cache/smarty/compile/26/7c/16/267c169b968f1f3a3b5d651baaf0b52c9b543f4e.file.header.tpl.php on line 167

 

 

It could be that it appeared first a few days after, because I didn't switch on error messages until then. This message disappears if I remove this code from header.tpl:

{$HOOK_displayHeadermenu}

But that's not the solution I'd like, since I would like that hook to appear in header. 

 

Questions:

1. Anyone who knows why I still can't transplant onto the new hook, even though I've added this to the module's php-file?

public function hookDisplayHeadermenu($params) 

    { return $this->hookDisplayTop('displayHeadermenu');   }

2. Will the message disappear when there's something transplanted onto the hook? Or how do I solve that one?

 

 

Thank you.