Sometimes you want to log to PHP’s error_log in a Symfony 2 app. This is useful if your app runs in a container (think Docker) and PHP’s error log is redirected to standard output and you want your application logs to show up there too.

You need to use at least version 2.4 of the MonologBundle to use the ErrorLogHandler:

{
    "require": {
        …
        "symfony/monolog-bundle": "~2.4"
    }
}

Then in your config_prod.yml and config_dev.yml change the type of the Monolog handlers to error_log and you are all set. For example, the Monolog config in config_dev.yml would look like this:

monolog:
    handlers:
        main:
            type:  error_log
            level: debug