Manual:Update.php

checks if the MediaWiki database schema need to be updated in order to work with the current version of MediaWiki. You should run  after each update of MediaWiki or after the update of an extension that requires a schema update (such as CheckUser).

Command line
From the command line, or an SSH shell or similar, change to the maintenance directory and execute the update script: $ php update.php

may exit with errors, leaving the database in an inconsistent state. Always backup the database before running the script!

From the browser
Since 1.17 you can browse to your config/index.php directory, it will detect that you already have a LocalSettings.php file and guide you through the update process.

Pre 1.17
If you can't (or don't wish to) run  from the command line, you can use MediaWiki's configuration script to force   to be run from a web browser. To do this:
 * 1) rename your LocalSettings.php file
 * 2) rename the config/LocalSettings.php file if it exits (script will not run if it exists)
 * 3) run the configuration script with the same settings as were used during the initial install, and then
 * 4) replace the newly created LocalSettings.php file with the old copy of the file that was renamed in step 1.

Options

 * --conf: provide configuration settings on the commandline
 * --quick: skip countdown sequence
 * --nopurge: do not purge objectcache table. Normally update.php purges the objectcache table in the database (generally contains the parser cache and the messages cache), if you don't want to purge this table, use the --nopurge</tt> option.