Split a domain name into keywords by creating a PHP function

General information for the website: Keyword separator
Description of requirements/features: Create a php function that returns the passed in string, with numbers/keywords separated by spaces, for a domain name.

It must return the entire string, no omissions. Eg, "barnesandnoble.com" returns "barnes and noble".
"247tv.org" returns "247 tv".

Domain list provided once accepted, or via message.

Sample code attached. I already have this integrated into a database, I've just created this sample code so you can work standalone.

The function will be processing around 30,000 domain names per day, so it needs to be efficient.

You may need to bolt in a dictionary. There may be multiple solutions, but the function needs to pick the best available/most likely.

eg. windowsteamblog.com could be;
- window steam blog
- windows team blog

The function needs to return the latter, "windows team blog".

Some resources to help with theory;
- http://stackoverflow.com/questions/3466972/how-to-split-a-string-into-words-ex-stringintowords-string-into-words
- http://stackoverflow.com/questions/1315373/programmatically-extract-keywords-from-domain-names

Please feel free to message questions before submitting a proposal.
Extra notes: Sample code attached. Sample domain list available on request. Note, the domains will change on a daily basis, there is no fixed algorithm - it can be any domain name.

You may need an English word dictionary.