Monolog: A powerful PHP log library that helps you improve application development and maintenance efficiency

Log recording is an indispensable part of the application development and maintenance cycle, and it depends not only on the recorded data, but also on the way it is recorded. This article will dive into the Monolog package to show how it can help you get the most out of your logs.

Core advantages:

• Widely Integrated: Monolog is a popular log library that integrates with most mainstream frameworks to facilitate developers to take advantage of its logging capabilities. It follows the PHP-FIG standard, making it easy to switch to other implementations.
• Flexible processing: Monolog supports multiple processors and bubbling mechanisms, allowing developers to record different types of messages to different outputs. It also supports sending log messages to external services, such as Slack, to notify the team when an error occurs.
• Functionally rich: Monolog provides a range of practical preprocessors for containing detailed information such as memory peaks, user IDs, and allows custom log message formats. This makes it a powerful tool for logging and debugging during application development/maintenance cycles.

Installation:

Monolog is available on Packagist and can be installed via Composer:

composer require 'monolog/monolog:1.13.*'

If you use a framework, Monolog usually provides an integration solution. The following example does not use framework integration and shows how to configure Monolog in any application.

Login logger:

When creating a logger, you should specify the channel name to distinguish the different loggers. The following example binds the logger to the application container:

// app/bootstrap/container.php

$logger = new \Monolog\Logger('general');
$app->container->logger = $logger;

Monolog follows the PSR-3 standard, making it easy to switch to other implementations. You can use the following methods for logging (log, debug, info, warning, error, critical, alert, emergency):

$app->container->logger->info("一條INFO消息。");

Processor:

Log messages will pass through the registered processor list. The processor needs to specify the log level and bubble state of the process (whether the message continues to be propagated). By default, Monolog uses MonologHandlerStreamHandler to log the log to standard error output. The available processors are listed in the documentation.

The following example demonstrates how to use multiple processors and bubbling mechanisms: log INFO messages to the browser console and error messages to terminal output.

// app/bootstrap/container.php

$logger = new \Monolog\Logger('general');

$browserHanlder = new \Monolog\Handler\BrowserConsoleHandler(\Monolog\Logger::INFO);
$streamHandler = new \Monolog\Handler\StreamHandler('php://stderr', \Monolog\Logger::ERROR);

$logger->pushHandler($browserHanlder);
$logger->pushHandler($streamHandler);

$app->container->logger = $logger;

// app/routes.php

$app->get('/admin/users', function () use ($app) {
    $app->container->logger->info("另一條INFO消息");
    $app->container->logger->error("另一條ERROR消息");
    // ...
});

Error messages are recorded to the terminal as expected, but why do they also appear in the browser console? This is Monolog's bubbling mechanism. The error message is first logged to the terminal and if the bubble option is set to true, it continues to propagate to the top of the processor queue. Set the bubbling option of streamHandler to false:

composer require 'monolog/monolog:1.13.*'

The error logs are now not displayed in the browser console, which is how to separate the log level.

Slack processor:

Before using the Slack processor, you need to obtain the token to authorize it to publish to the Slack channel.

// app/bootstrap/container.php

$logger = new \Monolog\Logger('general');
$app->container->logger = $logger;

You just need to specify the Slack token and channel name, the third optional parameter is the robot name. Slack's log level is CRITICAL, but you can change it using the setLevel method.

$app->container->logger->info("一條INFO消息。");

After sending a log message, you can access your channel to view recorded error messages.

// app/bootstrap/container.php

$logger = new \Monolog\Logger('general');

$browserHanlder = new \Monolog\Handler\BrowserConsoleHandler(\Monolog\Logger::INFO);
$streamHandler = new \Monolog\Handler\StreamHandler('php://stderr', \Monolog\Logger::ERROR);

$logger->pushHandler($browserHanlder);
$logger->pushHandler($streamHandler);

$app->container->logger = $logger;

Formatizer:

Each processor has a default formatter, if not specified, use LineFormatter. You can switch to other formatters such as HtmlFormatter.

// app/routes.php

$app->get('/admin/users', function () use ($app) {
    $app->container->logger->info("另一條INFO消息");
    $app->container->logger->error("另一條ERROR消息");
    // ...
});

The log messages will now be logged to the browser console in HTML format.

// app/bootstrap/container.php

// ...
$streamHandler = new \Monolog\Handler\StreamHandler('php://stderr', \Monolog\Logger::ERROR, false);
// ...

Preprocessor:

The preprocessor is used to add more details to the logs. For example, WebProcessor add more details about the request (URL, IP, etc.).

// app/bootstrap/container.php

// ...
$slackHandler = new \Monolog\Handler\SlackHandler('xoxp-5156076911-5156636951-6084570483-7b4fb8', '#general', 'ChhiwatBot');
$logger->pushHandler($slackHandler);

// ...

When logging, logging will pass through the registered processor list and you will get more details.

$slackHandler->setLevel(\Monolog\Logger::ERROR);

Summary:

Monolog is one of the excellent log libraries and integrates with most mainstream frameworks.

FAQ:

(The FAQ part is omitted here because the article is too long and has a high repetition of the main content of the article. If necessary, you can ask FAQ questions separately and I will answer them one by one.)

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