How to Print Log in Magento 2?

Logs in Magento 2 consist the system information for the future analysis.

To enable the debug mode go to Stores -> Configuration -> Advanced -> Developer -> Debug -> Set ‘Yes’ to Log to file.

Also make sure Magento store is in developer mode. If Magento store is in Production Mode then need run the below command.

php bin/magento config:set dev/debug/debug_logging 1

Below are the Methods to print Log in Magento 2.

Method 1 : Using Helper Data

File : app/code/V4U/Helloworld/Helper/Data.php

<?php

namespace V4U\Helloworld\Helper;

use \Magento\Framework\App\Helper\AbstractHelper;
use Zend\Log\Writer\Stream;
use Zend\Log\Logger;

class Data extends AbstractHelper
{
	public function printLog($log)
	{
       $writer = new Stream(BP . '/var/log/CustomLog.log');
       $logger = new Logger();
       $logger->addWriter($writer);
       $logger->info($log);
	}
}

<?php

namespace V4U\Helloworld\Helper;

use \Magento\Framework\App\Helper\AbstractHelper;

use Zend\Log\Writer\Stream;

use Zend\Log\Logger;

class Data extends AbstractHelper

{

public function printLog($log)

{

$writer = new Stream(BP . '/var/log/CustomLog.log');

$logger = new Logger();

$logger->addWriter($writer);

$logger->info($log);

}

Now you can call that Helper class where you want to print log.

File : app/code/[Vendor][Module][Path][fileName.php]

<?php 
namespace [Vendor]\[Module]\[Path];
use V4U\Helloworld\Helper\Data;

class FileName
{
	/**
     * The Helper Call From V4U Helloworld Module.
     *
     * @var Helper
     */

	protected $helper;

    public function __construct(Data $helperName)
    {
        $this->helper = $helperName;
    }

    $this->helper->printLog('msg for print'); /*Use this in Function to print log*/
}

<?php

namespace [Vendor]\[Module]\[Path];

use V4U\Helloworld\Helper\Data;

class FileName

{

/**

* The Helper Call From V4U Helloworld Module.

* @var Helper

protected $helper;

public function __construct(Data $helperName)

{

$this->helper = $helperName;

}

$this->helper->printLog('msg for print'); /*Use this in Function to print log*/

}

You can review log on following path : var/log/CustomLog.log

Method 2 : Using Logger Interface (Factory Method)

You can add Logger Interface where you want to print log.

File : app/code/[Vendor][Module][Path][fileName.php]

<?php

namespace [Vendor]\[Module]\[Path];
use Psr\Log\LoggerInterface;

class FileName
{
    /**
     * @var \Psr\Log\LoggerInterface
     */
    private $logger;
    
    public function __construct(LoggerInterface $logger;)
    {
        $this->logger = $logger;
    }

    $this->logger->debug('msg to print'); // print var\log\debug.log /*Use this in Function to print log*/
    $this->logger->info('msg to print');  // print var\log\system.log /*Use this in Function to print log*/
}

<?php

namespace [Vendor]\[Module]\[Path];

use Psr\Log\LoggerInterface;

class FileName

{

/**

* @var \Psr\Log\LoggerInterface

private $logger;

public function __construct(LoggerInterface $logger;)

{

$this->logger = $logger;

}

$this->logger->debug('msg to print'); // print var\log\debug.log /*Use this in Function to print log*/

$this->logger->info('msg to print'); // print var\log\system.log /*Use this in Function to print log*/

}

Method 3 : Using ObjectManager

For var\log\system.log

\Magento\Framework\App\ObjectManager::getInstance()->get('Psr\Log\LoggerInterface')->info('Write Here To Print Log - System Log');

1	\Magento\Framework\App\ObjectManager::getInstance()->get('Psr\Log\LoggerInterface')->info('Write Here To Print Log - System Log');

For var\log\debug.log

\Magento\Framework\App\ObjectManager::getInstance()->get('Psr\Log\LoggerInterface')->debug('Write Here To Print Log - Debug Log');

1	\Magento\Framework\App\ObjectManager::getInstance()->get('Psr\Log\LoggerInterface')->debug('Write Here To Print Log - Debug Log');

Method 4 : Temporary print log with new file

$myArrayVar = array("Vrajesh", "Patel");
$writer = new \Zend\Log\Writer\Stream(BP . '/var/log/CustomLogFile.log');
$logger = new \Zend\Log\Logger();
$logger->addWriter($writer);
$logger->info('Simple Text Log'); // To print Simple Text Log
$logger->info('Array Log'.print_r($myArrayVar, true)); // To print Array Log