Im looking to improve the search in one of my applications, where I sue regular fulltext searching, which isn't too bad, but Im looking to add some more complex behaviors, such as typo recognition and better relevancy.
Are there any solutions out there that can be integrated into an existing application? Im looking to search several tables in a single mysql DB, nothing complicated.
It has to work with non-apache servers (I use lighttpd).
Give a look to Zend_Search_Lucene it's a PHP5 port of the Apache Lucene project, the query language is very powerful.
I would say it depends on your current application. Zend Lucene could be a good alternative, but creating the index takes a very long time if there is a lot of data (and could kill your server).
Java Lucene is probably the best one but requires you to run tomcat.
Sphinx is also a good alternative but is a separate server with a PHP api (even a PECL extension) but has some drawback has it recreate the index every time you had something to it (at least the last time I checked it)
I think it probably worth an experimentation with a few solution first.
Zend_Search_LuceneOverview of both: "Sphinx and Lucene search engines, first impressions"