Upgrading from Yii 2.0

Update the application to the latest compatible Yii 2.0 release and apply its UPGRADE.md instructions before moving to Yii 22.0. Review UPGRADE-22.md and CHANGELOG.md in the framework package at the version you are installing; a development branch may contain changes absent from an earlier installation.

Runtime and dependencies

Use PHP 8.3 or later and check each extension’s compatibility with Yii 22.0. HHVM and CUBRID are no longer supported. Check the database server requirements before upgrading the framework.

Composer is the only class autoloader. Replace Yii::$classMap and Yii::autoload() usage with Composer mappings, load vendor/autoload.php from entry scripts, and regenerate the autoloader. See Autoloading.

Forms, widgets and assets

• Replace @bower asset paths with the required npm packages; @npm now defaults to @app/node_modules. Remove Bower requirements only after checking extensions that still depend on them;
• configure client-script strategies for forms, validators, grids and CAPTCHA. The yiisoft/yii2-jquery extension provides the jQuery implementations; custom strategies are also supported. Server validation remains available without either. See Client-side validation;
• review inline scripts: View::POS_READY and POS_LOAD use native DOM events and do not load jQuery or inject $. See Client scripts;
• set widget CSS classes explicitly or use a UI extension. Core form and grid defaults no longer supply Bootstrap classes, and ActionColumn no longer supplies Glyphicon markup;
• replace ApcCache with ApcuCache, remove useApcu, and replace removed cache backends and aliases listed in the installed upgrade guide. See Data caching.

Subclasses and actions

Compare custom overrides with their installed parent signatures, especially actions, condition builders, database schemas, MSSQL PDO wrappers and DbManager. Anonymous model classes must explicitly implement formName(). Removed deprecated methods and properties are enumerated in the installed UPGRADE-22.md.

Inline actions now invoke beforeRun() and afterRun(); remove duplicate manual calls. A false result from beforeRun() cancels execution. Module-level actions can have no controller; review shared filters and code that dereferences Action::$controller. See Standalone Actions.

Database behavior and existing data

Use UNION modifiers to sort or paginate a complete compound result. Ordinary orderBy(), limit() and offset() configure its first SELECT. Review generated-SQL assertions for the updated pagination, composite IN/NOT IN handling of NULL, and native SQLite upserts.

Active Record population now receives the query’s connection for schema reflection and typecasting. Forward the optional $db argument from overrides of populateRecord(), getTableSchema(), Query::populate() and ActiveQueryTrait::createModels(). attributes() and primaryKey() still use the model’s default connection unless overridden; supplying a query connection does not redefine that model metadata.

Back up existing data before applying database-specific migration instructions:

• MySQL/MariaDB defaults to utf8mb4 when no charset is configured; existing tables retain their previous charset. Review connection settings and table conversions separately. See Database connections;
• an explicitly configured PostgreSQL defaultSchema now sets the session search_path; review unqualified table names and matching pool configuration. Use structured builders for compound column alterations;
• MSSQL session tables need varbinary(max) for data; follow the installed guide when converting existing values;
• MSSQL RBAC schemas use different cascade handling. Inspect existing constraints and triggers before migrating;
• Oracle new auto-increment columns use native identity columns; existing sequence-and-trigger primary keys continue to work. Review custom Oracle parameter binding for the new native LOB path;
• reflected expression defaults now use yii\db\Expression across drivers. Review schema snapshots and ActiveRecord::loadDefaultValues() consumers, since saving such defaults can execute expressions;
• SQLite integrity changes cannot run inside a transaction or savepoint; place them outside that scope.

Run the application’s tests against every database it supports. Review form behavior, rendered classes, asset loading, authorization, session round trips, cache invalidation and logs after the upgrade. Yii 22.0 includes PSR-3 log adapters; avoid routing an external logger back into itself.