YII 提供的日志写入方法：
1、Yii::getLogger()->log($message, $level, $category = ‘application‘)
2、Yii::trace($message, $category = ‘application‘);
3、Yii::error($message, $category = ‘application‘);
4、Yii::warning($message, $category = ‘application‘);
5、Yii::info($message, $category = ‘application‘);
配置：
/config/web.php
components->log
默认配置：
‘log‘ => [ ‘traceLevel‘ => YII_DEBUG ? 3 : 0, ‘targets‘ => [ [ ‘class‘ => ‘yii\log\FileTarget‘, ‘levels‘ => [‘error‘, ‘warning‘], ], ], ],
现修改配置如下：
‘log‘ => [ ‘traceLevel‘ => YII_DEBUG ? 3 : 0, ‘targets‘ => [ [ ‘class‘ => ‘yii\log\FileTarget‘, ‘levels‘ => [‘error‘, ‘warning‘,‘info‘,‘trace‘], ], [ ‘class‘ => ‘yii\log\FileTarget‘, ‘levels‘ => [‘info‘], ‘categories‘ => [‘rhythmk‘], ‘logFile‘ => ‘@app/runtime/logs/Mylog/requests.log‘, ‘maxFileSize‘ => 1024 * 2, ‘maxLogFiles‘ => 20, ], ], ],
输出日志：
Yii::getLogger()->log("开始写自定义日志",Logger::LEVEL_ERROR);
Yii::trace("trace,开发调试时候记录");
Yii::error("error,错误日志");
Yii::warning("warning,警告信息");
Yii::info("info,记录操作提示");
输出自定义目录日志
// 日志文件在输出目录 @app/runtime/logs/Mylog/requests.log
Yii::info("info .... ","rhythmk");
原文：http://www.cnblogs.com/sandea/p/5616356.html