Since big web applications came into existence, searching for data (and doing it lightning fast and accurate) has been one of the most important problems in web applications
I would suggest that you look at Solr, which is a best practice implementation of Lucene. Solr uses a REST based API that also has a very good PHP client. This will allow you to leverage the power of Lucene without needing to perform any of the low level programming to get the NLP power that you want. Also, you would probably want to grab the trunk version of Solr as the NLP development is very active right now and new capabilities are being added every day.