Forum How to use replacement variables?

[محروم.كوم]

In the registration "welcome" mail I need the URL of the server as a clickable link. Not the URL of the forum, which is $vboptions[bburl] but the servername alone. I made a replacement variable called 'serverurl' that contains the PHP code for the server name:
Code:
http://
The vBulletin manual talks about advantages and dangers of replacement variables but I cannot find an example how to actually use them. I tried my replacement variable in the phrase of the welcome mail in various flavours:
[serverurl]
$vboptions[serverurl]

etc, nothing worked.


How do I call a replacement variable?
Can I have PHP code in a replacement variable?
Is there another method to get just the URL of the server? __DEFINE_LIKE_SHARE__