[Michael Morris]

You don't need to mess with PHP for this in vbulletin. Create the user profile field using the user profile field manager. Once you create it note the field number. You can then referrence the field in templates using <if condition="$bbuserinfo['fieldX']">do this<else />do this</if>

If you need to refer to it in the post bit for the profile of that poster use $post['fieldX'] instead.

For more information regarding user profile fields check this part of the manual: http://www.vbulletin.com/docs/html/profile