2019/01/14 12:04:51 [error] 21549#21549: *3558 FastCGI sent in stderr: "PHP message: PHP Fatal error: Class SphinxMWSearch contains 2 abstract methods and must therefore be declared abstract or implement the remaining methods (SearchDatabase::doSearchTextInDB, SearchDatabase::doSearchTitleInDB) in /var/opt/www/extensions/SphinxSearch/SphinxMWSearch.php on line 15" while reading response header from upstream, client: 192.168.122.1, server: wiki.yuyizhi.org, request: "GET /index.php?title=Special:%E6%90%9C%E7%B4%A2&search=sphinx HTTP/1.0", upstream: "fastcgi://unix:/var/run/php-fpm/php5-fpm.sock:", host: "wiki.yuyizhi.org"
Topic on Extension talk:SphinxSearch
The SearchDatabase class that SphinxSearch extends was changed from REL1_31 to REL1_32. It now requires you to define doSearchTextInDB and doSearchTitleInDB methods.
See REL1_31 https://doc.wikimedia.org/mediawiki-core/REL1_31/php/classSearchDatabase.html vs REL1_32 https://doc.wikimedia.org/mediawiki-core/REL1_32/php/classSearchDatabase.html
This is sortof mentioned in the patch notes if you search for Search under deprecation (note this is a Backwards compatibility break instead) https://www.mediawiki.org/wiki/Release_notes/1.32#Compatibility:
> Overriding SearchEngine::{searchText,searchTitle,searchArchiveTitle} in extending classes is deprecated. Extend related doSearch* methods instead.
If you are like me and not comfortable fixing the extension yourself, you will have to wait for one of the extension contributors to update the extension to work with REL1_32. Until then you will have to stay on REL1_31 if you wish to use the extension.
A patch has been submitted to fix this issue: https://gerrit.wikimedia.org/r/536787
Patch has been merged to master, so if you get the extension code from git, it should already work. Still figuring out how to backport recent fixes into REL1_33 and below.