Magento 2 uses monolog library to log messages. You can check this library in following path location in magento 2.
<magento_root_folder>/vendor/monolog/
Log file will be created inside var/log folder
If you want to use log in your custom module, you need to add instance of monolog class in your custom file class. You need to pass the instance in the constructor of your custom class.
Go to app/code/yourCompany/yourModule/Block/custom.php
add following protected variable in custom file class.
/** * @var \Psr\Log\LoggerInterface */ protected $_logger;
add following parameter in your custom class __construct()
\Psr\Log\LoggerInterface $logger
Now, we need to create an object
$this->_logger = $logger;
$this->_logger->addDebug('some text or variable');
Finally, constructor function looks like following
public function __construct(
\Magento\Framework\View\Element\Context $context,
\Magento\Cms\Model\Page $page,
\Magento\Cms\Model\Template\FilterProvider $filterProvider,
\Magento\Store\Model\StoreManagerInterface $storeManager,
\Magento\Cms\Model\PageFactory $pageFactory,
\Magento\Framework\View\Page\Config $pageConfig,
\Psr\Log\LoggerInterface $logger,
array $data = []
) {
parent::__construct($context, $data);
// used singleton (instead factory) because there exist dependencies on \Magento\Cms\Helper\Page
$this->_page = $page;
$this->_filterProvider = $filterProvider;
$this->_storeManager = $storeManager;
$this->_pageFactory = $pageFactory;
$this->pageConfig = $pageConfig;
$this->_logger = $logger;
$this->_logger->addDebug('some text or variable');
}
Here is the use of some predefined examples :
$this->_logger->addDebug($message); // log location: var/log/system.log $this->_logger->addInfo($message); // log location: var/log/exception.log $this->_logger->addNotice($message); // log location: var/log/exception.log $this->_logger->addError($message); // log location: var/log/exception.log $this->_logger->critical($e); // log location: var/log/exception.log
You can also write to the logs using the zend library
$writer = new \Zend\Log\Writer\Stream(BP . '/var/log/test.log');
$logger = new \Zend\Log\Logger();
$logger->addWriter($writer);
$logger->info('Your text message');
