Fatal Error on editing joomla articles

-- url of the page with the problem -- : glasgowcreative.co.uk
-- HikaShop version -- : 1.5.4 - business version
-- Joomla version -- : 2.5
-- PHP version -- : 5.3.22
-- Browser(s) name and version -- : firefox 25.0.1


When I try to edit any article in Joomla, I get a short set of Edit Article options on a white screen and then the following:
" Call to undefined function hikashop_getFormToken() in /home/glasgowc/public_html/plugins/editors-xtd/hikashopproduct/hikashopproduct.php line 103 "

Line 103 in the file is:
$link = 'index.php?option=com_hikashop&ctrl=plugins&task=trigger&function=productDisplay&tmpl=component&cid='.$plugin->extension_id.'&'.hikashop_getFormToken().'=1';

Any help is much appreciated.
Regards,
Christy

Thanks for the response Nicolas,

I have done that, but it's giving me the same error. This is what I now have for lines 24-30 of the PHP doc:

function onDisplay($name, $asset='', $author=''){
$extension = JRequest::getCmd('option');
if ($extension=='com_content'){
if(!defined('DS'))
define('DS', DIRECTORY_SEPARATOR);
if(!include_once(rtrim(JPATH_ADMINISTRATOR,DS).DS.'components'.DS.'com_hikashop'.DS.'helpers'.DS.'helper.php')) return true;
if(version_compare(JVERSION,'1.6.0','<')){


Thanks,
Christy

Hi Nicolas,
This is the error I am getting now. The previous error was line 103, now it's 106, but I'm thinking it's because I added the 3 lines of code.

Fatal error: Call to undefined function hikashop_getFormToken() in /home/glasgowc/public_html/plugins/editors-xtd/hikashopproduct/hikashopproduct.php on line 106

Thanks,
Christy

Hi,

Can you download the last Hikashop version through our website, install it, and test it again ?

Note that making a backup is always a good security.

Thank you, that has fixed the issue.

Cheers,
Christy