uninitialised variables and E_NOTICE

 missed that an E_NOTICE is emitted if an uninitialised variable is accessed
Thanks for pointing out the typo. As you can see from the diff, the text with "somehow..." was already there, I did not intend to change it by this pull request but it would surely be a good idea to improve it as well. 
About the second question: doing `$a = $b;` will define $b, it exist as variable and can be used from that point on without further E_NOTICEs. So I guess the person who wrote the sentence "Somehow..." meant that $b is defined but not  initialised in the sense of it contains `NULL`. But that is just a guess.