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WikiFarmMultiVersion is a small but critical class in MultiVersion.php that provides a fast-path mechanism for per-wiki MediaWiki version overrides. While the farm’s primary version data lives in the databases.php CreateWiki cache, that cache is rebuilt asynchronously. WikiFarmMultiVersion bridges the gap by maintaining a lightweight PHP file — wikiVersions.php — that is read on every request and takes precedence over whatever is stored in the databases cache. This means a version change made through Special:ManageWiki/core is visible to the web server on the very next request, without waiting for a full cache regeneration.
The ManageWiki UI forms (onManageWikiCoreAddFormFields / onManageWikiCoreFormSubmission) that surface the version selector are handled by MirahezeFunctions, not by this class. WikiFarmMultiVersion is solely responsible for the on-disk fast-path file.

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VERSIONS_FILE Constant

ConstantValue
VERSIONS_FILE/srv/mediawiki/config/wikiVersions.php
This file is the single source of truth for per-wiki version overrides. It is a PHP file that returns an associative array keyed by database name. The file is read with @include (suppressing errors on a missing file) and written atomically using a temp-file and rename().

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File Format

<?php
/**
 * Per-wiki MediaWiki version overrides.
 * Managed automatically by WikiFarmMultiVersion::setWikiVersion().
 */
return [
    'examplewiki' => '1.45',
    'anotherwiki' => '1.46',
];
Only wikis with a version different from the farm default appear in this file. When a wiki’s override is removed (by passing null or the default version to setWikiVersion()), its entry is deleted from the file rather than set to the default value.

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Static Methods

Signature: public static function getWikiVersion( string $dbname ): stringReads wikiVersions.php and returns the stored version for $dbname. If the file does not exist, cannot be parsed, or does not contain an entry for $dbname, falls back to the farm default version by resolving:
MirahezeFunctions::MEDIAWIKI_VERSIONS[
    MirahezeFunctions::getDefaultMediaWikiVersion()
]
ParameterTypeDescription
$dbnamestringThe wiki’s database name (e.g. examplewiki)
Returns: string — A version number string such as '1.45' or '1.46'.Example:
$version = WikiFarmMultiVersion::getWikiVersion( 'examplewiki' );
// Returns '1.45' if overridden, or the farm default otherwise
Signature: public static function setWikiVersion( string $dbname, ?string $version ): voidAtomically writes a new version mapping for $dbname into wikiVersions.php. The write is performed using a process-specific temp file (wikiVersions.php.tmp.<pid>) that is then rename()d over the target, preventing any request from reading a partially-written file during concurrent access.After writing, the method invalidates the wiki’s per-wiki CreateWiki cache file (cw_cache/{dbname}.php) by deleting it, ensuring the next request rebuilds from fresh data.
ParameterTypeDescription
$dbnamestringThe wiki’s database name
$versionstring|nullThe version string to set (e.g. '1.46'), or null to remove the override and revert to farm default
Passing null or the farm default removes the override entirely:
// Set a specific version
WikiFarmMultiVersion::setWikiVersion( 'examplewiki', '1.46' );

// Remove the override — wiki reverts to farm default
WikiFarmMultiVersion::setWikiVersion( 'examplewiki', null );
The temp-file + rename pattern is safe for concurrent web requests but assumes the filesystem supports atomic renames (which is true for all standard Linux filesystems). Do not write directly to wikiVersions.php by hand — always use this method to avoid leaving the file in a partially-written state.
Signature: public static function onCreateWikiPhpBuilder( string $dbname, array &$cacheData ): voidThis is a hook handler for the CreateWikiPhpBuilder hook fired by the CreateWiki extension when it rebuilds the databases.php cache for a wiki. It reads wikiVersions.php and, if an override exists for $dbname, injects it as the 'v' key into $cacheData by reference. This keeps the databases cache in sync with the fast-path file so that MirahezeFunctions::getMediaWikiVersion() sees the same version regardless of which source it checks first.
ParameterTypeDescription
$dbnamestringThe wiki being rebuilt
$cacheDataarray&The cache data array being written; modified in place
The injected 'v' key overrides any version previously stored in the wiki_extra JSON column of cw_wikis.

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Integration with MirahezeFunctions

MirahezeFunctions::getMediaWikiVersion() checks wikiVersions.php before reading the databases.php cache, implementing this resolution chain:
1

Environment override

If the MIRAHEZE_WIKI_VERSION environment variable is set, that value is used unconditionally.
2

wikiVersions.php fast-path

wikiVersions.php is included and checked for the current database name. If found, that version is returned immediately — no cache file read is needed.
3

databases.php cache

The 'v' key from the wiki’s entry in databases.php is used. This value is kept current by the onCreateWikiPhpBuilder hook.
4

Farm default

Falls back to MEDIAWIKI_VERSIONS[getDefaultMediaWikiVersion()] — '1.45' on production, '1.45' on staging.

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ManageWiki Integration

Version changes are surfaced to administrators via Special:ManageWiki/core, which shows a mediawiki-version select field populated by onManageWikiCoreAddFormFields() in MirahezeFunctions. Only users with the managewiki-restricted right can change a wiki’s MediaWiki version.
When a version change is submitted, onManageWikiCoreFormSubmission() calls WikiFarmMultiVersion::setWikiVersion() for the immediate fast-path update, and also stores the value persistently via ManageWikiCore::setExtraFieldData() so it survives a full cache rebuild.
If you need to force a wiki back to the farm default version without going through the UI, delete the entry from wikiVersions.php by calling WikiFarmMultiVersion::setWikiVersion( 'yourwiki', null ) from the CLI.

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