| base | optional base class for search plugins providing simple caching based on ACM and functions to retrieve ignore_words and synonyms |
| fulltext_mysql | Fulltext search for MySQL |
| fulltext_native | phpBB's own db driven fulltext search, version 2 |
| fulltext_postgres | Fulltext search for PostgreSQL |
| fulltext_sphinx | Fulltext search based on the sphinx search deamon |