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Using the Logger

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Using the Logger

The Console component comes with a standalone logger complying with the PSR-3 standard. Depending on the verbosity setting, log messages will be sent to the OutputInterface instance passed as a parameter to the constructor.

The logger does not have any external dependency except psr/log. This is useful for console applications and commands needing a lightweight PSR-3 compliant logger:

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namespace Acme;

use Psr\Log\LoggerInterface;

class MyDependency
{
    private $logger;

    public function __construct(LoggerInterface $logger)
    {
        $this->logger = $logger;
    }

    public function doStuff()
    {
        $this->logger->info('I love Tony Vairelles\' hairdresser.');
    }
}

You can rely on the logger to use this dependency inside a command:

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namespace Acme\Console\Command;

use Acme\MyDependency;
use Symfony\Component\Console\Command\Command;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;
use Symfony\Component\Console\Logger\ConsoleLogger;

class MyCommand extends Command
{
    protected function configure()
    {
        $this
            ->setName('my:command')
            ->setDescription(
                'Use an external dependency requiring a PSR-3 logger'
            )
        ;
    }

    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $logger = new ConsoleLogger($output);

        $myDependency = new MyDependency($logger);
        $myDependency->doStuff();
    }
}

The dependency will use the instance of ConsoleLogger as logger. Log messages emitted will be displayed on the console output.

Verbosity

Depending on the verbosity level that the command is run, messages may or may not be sent to the OutputInterface instance.

By default, the console logger behaves like the Monolog's Console Handler. The association between the log level and the verbosity can be configured through the second parameter of the ConsoleLogger constructor:

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use Psr\Log\LogLevel;
// ...

$verbosityLevelMap = [
    LogLevel::NOTICE => OutputInterface::VERBOSITY_NORMAL,
    LogLevel::INFO   => OutputInterface::VERBOSITY_NORMAL,
];

$logger = new ConsoleLogger($output, $verbosityLevelMap);

Color

The logger outputs the log messages formatted with a color reflecting their level. This behavior is configurable through the third parameter of the constructor:

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// ...
$formatLevelMap = [
    LogLevel::CRITICAL => ConsoleLogger::ERROR,
    LogLevel::DEBUG    => ConsoleLogger::INFO,
];

$logger = new ConsoleLogger($output, [], $formatLevelMap);

Errors

The Console logger includes a hasErrored() method which returns true as soon as any error message has been logged during the execution of the command. This is useful to decide which status code to return as the result of executing the command.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.