虽然我不懂 Ruby 和 ROR，不过在当初接触的时候就感觉 ROR 的多数据库配置是一个很棒的想法，之前由于忙碌没有来做，昨天看到 lzyy 在博客上面发布了自己的实现想法，感觉还是有些麻烦，今天自己做了另外一种方法：

1. 扩展 Kohana 数据库类(libraries/MY_Database.php)

class Database extends Database_Core {
 	
	/**
	 * Multiway profile of Database configures
	 */
	public function __construct()
	{
		$config = array();
		
		// custom environment key to databse config.
		$environment = Kohana::config('database.environment');
		// available: development, test, pro
		
		if ( !is_array($environment) && !empty($environment) )
		{
			$config = Kohana::config('database.'.$environment);
		}
		
		parent::__construct($config);
	}
}

2. 修改 config/databse.php

// Sets the default databse config to "development"
$config['environment'] = 'development';


// original Kohana database config
$config['default'] = array
(
	'benchmark'     => TRUE,
	'persistent'    => FALSE,
	'connection'    => array
	(
		'type'     => 'mysql',
		'user'     => 'dbuser',
		'pass'     => 'p@ssw0rd',
		'host'     => 'localhost',
		'port'     => FALSE,
		'socket'   => FALSE,
		'database' => 'database_name'
	),
	'character_set' => 'utf8',
	'table_prefix'  => '',
	'object'        => TRUE,
	'cache'         => FALSE,
	'escape'        => TRUE
);


// Development
$config['development'] = array
(
	'benchmark'     => TRUE,
	'persistent'    => FALSE,
	'connection'    => array
	(
		'type'     => 'mysql',
		'user'     => 'dbuser',
		'pass'     => 'p@ssw0rd',
		'host'     => 'localhost',
		'port'     => FALSE,
		'socket'   => FALSE,
		'database' => 'database_name'
	),
	'character_set' => 'utf8',
	'table_prefix'  => '',
	'object'        => TRUE,
	'cache'         => FALSE,
	'escape'        => TRUE
);


// Test online
$config['test'] = array
(
	'benchmark'     => TRUE,
	'persistent'    => FALSE,
	'connection'    => array
	(
		'type'     => 'mysql',
		'user'     => 'dbuser',
		'pass'     => 'p@ssw0rd',
		'host'     => 'localhost',
		'port'     => FALSE,
		'socket'   => FALSE,
		'database' => 'database_name'
	),
	'character_set' => 'utf8',
	'table_prefix'  => '',
	'object'        => TRUE,
	'cache'         => FALSE,
	'escape'        => TRUE
);


// Production online
$config['production'] = array
(
	'benchmark'     => TRUE,
	'persistent'    => FALSE,
	'connection'    => array
	(
		'type'     => 'mysql',
		'user'     => 'dbuser',
		'pass'     => 'p@ssw0rd',
		'host'     => 'localhost',
		'port'     => FALSE,
		'socket'   => FALSE,
		'database' => 'database_name'
	),
	'character_set' => 'utf8',
	'table_prefix'  => '',
	'object'        => TRUE,
	'cache'         => FALSE,
	'escape'        => TRUE
);

$config['default'] 数组并没有移除，这是为了保证配置在默认情况下不报错。

同时我已经把此功能提交到了官方，希望在今后的版本可以采用：http://dev.kohanaphp.com/issues/1915

Source:
MY_Database.php:http://code.google.com/p/kohana-fans-cn/source/browse/trunk/libraries/MY_Database.php
config/database.php:http://code.google.com/p/kohana-fans-cn/source/browse/trunk/config/database.php