thanks nicolas for your patience.
I think i was not clear on my question. i was already successful with adding the joomla user id manually to my uddeim link. But it would be nice to get it using a button that will query the joomla user id.
My problem is how to get the joomla user id or user_cms_id from the product page and vendor page.
Everytime i execute the code you have given nothing happens. i used a different code using PHP inside html. i did not post it since you have given me a better one.
Now, to check if i am doing the code right i added the button to the code you have given me. i have posted this code below to check if it will echo the user id only and not to redirect to uddeim. But nothing happens.
<?php
$userClass = hikashop_get('class.user');
$user = $userClass->get($vendor->vendor_admin_id);
echo "<a href='$user->user_cms_id'>test</a>";
?>
Anyway, thanks again to your code but its still not working. i dont see a number or any user id next to the equal sign.
This is the code i used.
<?php
$userClass = hikashop_get('class.user');
$user = $userClass->get($vendor->vendor_admin_id);
echo '<a href="/index.php?option=com_uddeim&task=new&recip='.$user->user_cms_id.'">test</a>';
?>
The url below is the result. It is still empy
http://.../index.php?option=com_uddeim&task=new&recip=
Thanks again for you patience.