Web - Server

Hi,

I have a question regarding the given source in the excercise "SQL Injection - Routed" (http://repository.root-me.org/Exploitation%20-%20Web/EN%20-%20Routed%20SQL%20Injection%20-%20Zenodermus%20Javanicus.txt).

After the two minus characters (—) the writer adds an additional plus (—+).

Why does he do that? What is the meaning of adding it to the sql injection? I understand the two minus characters but not why the additional plus sign.