Yii2 logging: targets, configuration, and VarDumper

Available log targets:

Target	Destination
`yii\log\DbTarget`	A database table.
`yii\log\EmailTarget`	Email, using an address configured in advance.
`yii\log\FileTarget`	A file.
`yii\log\SyslogTarget`	syslog, via the `syslog()` function.

Configuration

'log' => [
    'traceLevel' => YII_DEBUG ? 3 : 0,
    'targets' => [
        [
            'class' => 'yii\log\FileTarget',
            'levels' => ['error', 'warning'],
        ],
    ],
],

Next to levels you can add the variables to dump with every message:

'logVars' => ['_GET', '_POST'],

Or simply (my favourite option):

'logVars' => [],

This strips noise like $_SERVER and $_COOKIE from the log entries.

Writing to the log

Yii::info('Displaying the whole list of cars.');

Flushing immediately

Because of the flushing and exporting level settings, calling Yii::debug() or any other logging method does not write the message to the target immediately. This can be a problem for long-running console applications. To make each message appear right away, set both flushInterval and exportInterval to 1:

return [
    'bootstrap' => ['log'],
    'components' => [
        'log' => [
            'flushInterval' => 1,
            'targets' => [
                [
                    'class' => 'yii\log\FileTarget',
                    'exportInterval' => 1,
                ],
            ],
        ],
    ],
];

Stack traces

You can log the call path where the error happened:

'log' => [
    'traceLevel' => 10,
    // ...

The output is primitive but sometimes useful:

2019-09-04 15:21:07 [-][-][-][error][application] Process stopped: Hello error!
    in /var/www/app/models/Spreadsheet.php:313
    in /var/www/app/models/Spreadsheet.php:123
    in /var/www/app/commands/AppController.php:21

Sending logs by email

'components' => [
    'log' => [
        'flushInterval' => 1,
        'targets' => [
            [
                'class' => 'yii\log\EmailTarget',
                'exportInterval' => 1,
                'mailer' => 'mailer',
                'levels' => ['error'],
                'message' => [
                    'from'    => 'robot@example.com',
                    'to'      => 'developer@example.com',
                    'subject' => 'Error log message [App]',
                ],
            ],
        ],
    ],
],

VarDumper helper

yii\helpers\VarDumper is a safer alternative to var_dump() for objects with recursive references.

Print a variable:

VarDumper::dump($var);

Return the dump as a string:

VarDumper::dumpAsString($var);