It might also be a good time to try a few more editors.  If you think PHP might be something you will do a lot of in the future try the PHP flavour of Eclipse.  It might be easier to stay with Notepad++ for now but start to experiment (even if it is with Notepad++ add-ons).

Do a search and you will find plenty of editors.  Maybe also check out some forums on Web development for the opinions of other developers.  Be aware that everyone is different and so just because twenty people agree that vi is the best editor doesn't mean it will suit you.