The Doctrine Migration tools allow you to migrate databases and it issues alter table statements directly to your databases when you need to deploy database changes.

++ Writing Migration Classes

Migration classes consist of a simple class that extends from Doctrine_Migration. You can define a public up() and down() method that is meant for doing and undoing changes to a database for that migration step.

<code type="php">
class MigrationTest extends Doctrine_Record
{
    public function setTableDefinition() 
    {
        $this->hasColumn('field1', 'string');
    }
}

class Migration2 extends Doctrine_Migration
{
    public function up()
    {
        $this->createTable('migration_test', array('field1' => array('type' => 'string')));
    }
    
    public function down()
    {
        $this->dropTable('migration_test');
    }
}

class Migration3 extends Doctrine_Migration
{
    public function up()
    {
        $this->addColumn('migration_test', 'field1', 'string');
    }
    
    public function down()
    {
        $this->renameColumn('migration_test', 'field1', 'field2');
    }
}

class Migration4 extends Doctrine_Migration
{
    public function up()
    {
        $this->changeColumn('migration_test', 'field1', 'integer');
    }
    
    public function down()
    {
        $this->changeColumn('migration_test', 'field1', 'string');
    }  
}
</code>

+++ Methods

Here is a list of the available methods you can use to alter your database in your migration classes

<code type="php">
public function createTable($tableName, array $fields = array(), array $options = array())
public function dropTable($tableName)
public function renameTable($oldTableName, $newTableName)
public function addColumn($tableName, $columnName, $type, array $options = array())
public function renameColumn($tableName, $oldColumnName, $newColumnName)
public function changeColumn($tableName, $columnName, $type, array $options = array())
public function removeColumn($tableName, $columnName)
public function addIndex($tableName, $indexName, array $options = array())
public function removeIndex($tableName, $indexName)
</code>

+++ Altering Data

You can alter table directly in your up() and down() methods like you normally would by creating new model instances and calling save() or creating queries and deleting data.

<code type="php">
class Migration1 extends Doctrine_Migration
{
    public function up()
    {
        // Add new user
        $user = new User();
        $user->loginname = 'jwage';
        $user->save();
    }
    
    public function down()
    {
        // Delete the user we added in the up
        $query = new Doctrine_Query();
        $query->delete('User')->from('User u')->where('u.loginname = ?', 'jwage')->execute();
        
    }
}
</code>

++ Performing Migrations

<code type="php">
// Upgrade one at a time
Doctrine_Migration::migration(1, 2);
Doctrine_Migration::migration(2, 3);
Doctrine_Migration::migration(3, 4);

// Then revert back to version 1
Doctrine_Migration::migration(4, 1);

// One big upgrade
Doctrine_Migration::migration(1, 4);

echo Doctrine_Migration::getCurrentVersion(); // should echo 4
</code>