Searching for hydrolocked brings up two threads for me.
As i say its contextual, so to search whole forum search from forum page, to search a topic do it from topic page, to search a section do it from section page.
or use the full search by using the menu.
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im not sure what you mean by dictionary based search?
php based search is very different to html based search.
On a html site, you put in a search term, and the site then scans every single html page looking for that search search term, and produces the results (results are cached to help with speed)
on a php based site such as this everything is stored in a database, so the search tool scans the database to then find the relevant topics. now obviously it doesnt scan the entire database. A large forum with say 500,000 posts, that would be 500,000 database entries it would have to scan. So instead, all the key words are pre stored in a single database table.
How accurate that search is depends on how big we specify the table to be. A small table, may only include a handful of keywords from each post, a larger table we may specify all words except connectives (and, if, of etc) to be stored. Or on a large table we may specify it store everything.
Of course the larger the table the more accurate the search.
Countered by, the larger the table the slower the search (and the slower the site as its doing extra php calls when users search).