How do I use migrations in Yii to manage database schema changes?
Jun 27, 2025 am 12:17 AM
Migrations in Yii are PHP classes used to manage and version-control database schema changes, allowing developers to safely apply, track, and revert updates across different environments. They help maintain consistency when working in teams or deploying to multiple servers. To create a migration, use the command yii migrate/create [name], which generates a timestamped file under the migrations/ directory. Inside this file, define the up() method to apply changes and down() to reverse them, ensuring both methods correctly correspond for safe rollbacks. After writing migrations, run them using yii migrate or yii migrate/up, and roll back with yii migrate/down or yii migrate/to [timestamp] to revert to a specific version. Yii tracks executed migrations in a table named migration, preventing duplicate runs and enabling smooth setup of new environments by replaying all necessary changes. Always test migrations locally before sharing or deploying to production.
When you need to manage database schema changes in a Yii application, migrations are your go-to tool. They let you version-control your database structure just like you do with code, making it easier to collaborate and deploy updates safely.
What Are Migrations in Yii?
Migrations are PHP classes that help you apply and revert changes to your database schema. In Yii, they're especially useful when working in teams or deploying to multiple environments (like dev, staging, and production). Each migration file represents a version of your database schema and contains instructions to upgrade or downgrade it.
For example, if you want to add a new table for user profiles, you'd create a migration that defines how to create the table and also how to drop it if needed later.
How to Create a Migration
You can generate a new migration using the migrate/create command from the console:
yii migrate/create create_profile_table
This creates a new PHP file under the migrations/ directory. The filename starts with a timestamp so Yii knows which order to apply them in.
Inside this file, you'll find two main methods:
up()– applies the migrationdown()– reverts it
Here's a simple example that creates a profile table:
public function up()
{
$this->createTable('profile', [
'id' => $this->primaryKey(),
'user_id' => $this->integer()->notNull(),
'bio' => $this->text(),
]);
}
public function down()
{
$this->dropTable('profile');
}Make sure your logic in down() truly reverses what up() does — otherwise, unexpected issues might pop up when rolling back.
Running and Rolling Back Migrations
Once you've written your migration, run it using:
yii migrate/up
To apply all pending migrations at once, just use:
yii migrate
If something goes wrong or you need to undo recent changes, Yii lets you roll back specific migrations:
yii migrate/down
Or, if you want to revert all migrations up to a certain point:
yii migrate/to 150101_000000
Replace the timestamp with the one from the target migration file.
Yii keeps track of applied migrations in a table called migration, so it knows which ones have already been run. If you're setting up a fresh environment, just run all migrations again — Yii will apply only the ones not yet recorded.
That's the core workflow. It's straightforward once you get used to writing schema changes as PHP code. Just remember to test each migration locally before pushing to shared branches or production.
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