yii2-swiftmailer/docs/guide/logging.md

Logging

Yii provides flexible and extensible logger that is able to handle messages according to serverity level or their type. You may filter messages by multiple criteria and forward them to files, email, debugger etc.

Logging basics

Basic logging is as simple as calling one method:

\Yii::info('Hello, I am a test log message');

Message category

Additionally to the message itself message category could be specified in order to allow filtering such messages and handing these differently. Message category is passed as a second argument of logging methods and is application by default.

Severity levels

There are multiple severity levels and corresponding methods available:

• \Yii::trace used maily for development purpose to indicate workflow of some code. Note that it only works in development mode when YII_DEBUG is set to true.
• \Yii::error used when there's unrecoverable error.
• \Yii::warning used when an error occured but execution can be continued.
• \Yii::info used to keep record of important events such as administrator logins.

Log targets

When one of the logging methods is called, message is passed to \yii\log\Logger component also accessible as Yii::$app->log. Logger accumulates messages in memory and then when there are enough messages or when current request finishes, sends them to different log targets, such as file or email.

You may configure the targets in application configuration, like the following:

[
	'components' => [
		'log' => [
			'targets' => [
				'file' => [
					'class' => 'yii\log\FileTarget',
					'levels' => ['trace', 'info'],
					'categories' => ['yii\*'],
				],
				'email' => [
					'class' => 'yii\log\EmailTarget',
					'levels' => ['error', 'warning'],
					'message' => [
						'to' => ['admin@example.com', 'developer@example.com'],
						'subject' => 'New example.com log message',
					],
				],
			],
		],
	],
]

In the config above we are defining two log targets: \yii\log\FileTarget and \yii\log\EmailTarget. In both cases we are filtering messages handles by these targets by severity. In case of file target we're additionally filter by category. yii\* means all categories starting with yii\.

Each log target can have a name and can be referenced via the targets property as follows:

Yii::$app->log->targets['file']->enabled = false;

When the application ends or flushInterval is reached, Logger will call flush() to send logged messages to different log targets, such as file, email, Web.

Configuring context information

Profiling

TBD

• Yii::beginProfile()
• Yii::endProfile()