The development policy defines how Wikimedia software is developed and maintained. This includes MediaWiki core, the bundled skins and extensions, as well as other skins and extensions that are deployed on Wikimedia Foundation wikis.
All Wikimedia engineering endeavors are guided by the Architecture principles.
Creation of new services that are external to MediaWiki, should follow the Services policy
Changes to PHP support in MediaWiki core or components bundled with official MediaWiki releases, must follow the Support policy for PHP.
Privileged Gerrit users must follow the Gerrit privilege policy when exercising their +2 rights.
Changes to MediaWiki core that have impact on extensions must follow the Stable interface policy.
Database queries and schema changes must follow the MediaWiki database policy.
PHP's built in serialization mechanism (the
unserialize() functions) should not be used for data stored (or read from) outside of the current process (RFC T161647).
See also the relevant section of the PHP coding convention.