Multiple update statements

I'm maintaining someone else's code. Application is written in PHP with
MS SQL database. Driver installed is FreeTDS 0.64. Platform Solaris 10
x86.

I came across this query:
mssql_query("UPDATE user_project SET membership=43 WHERE project=49 AND
usernum=2UPDATE user_project SET membership=0 WHERE project=49 AND
usernum=9UPDATE user_project SET membership=0 WHERE project=49 AND
usernum=10UPDATE user_project SET membership=0 WHERE project=49 AND
usernum=12UPDATE user_project SET membership=0 WHERE project=49 AND
usernum=14UPDATE user_project SET membership=0 WHERE project=49 AND
usernum=15UPDATE user_project SET membership=0 WHERE project=49 AND
usernum=16")

What is interesting is that records that don't exist are inserted :) If
I had an empty user_project table, after the execution of the above
query I would have 7 new records in user_project.

I would like to know whether this is expected and documented somewhere.

Thanks