Rudi, Well, your new developer should also join this mailing list. Mailing lists are good resources for asking questions to a group that is pretty responsive.
Blogs, Forums, Mailing Lists, User Groups, Books, Conferences, and a willingness to learn. That is how you probably learn any language these days. Some of those items have a high monetary cost, but many times if you get that "one" thing from anyone of those then the cost was justified. How your developer learns is unique to the individual. Have you sat down and asked him or her learn PHP? Translate their personal successes into a training plan to repeat the same success. ColdFusion has a certification program. You can set this up as a 9-12 month goal, as an example. Teddy