Where are PHP Errors Logged?
So when we encounter errors in our code, where exactly can we find them? At a high level, there are really only three places where PHP errors can be found: inline with program execution, in the system log, or in error monitoring tools like Rollbar.
By default, whenever an error or exception is thrown, PHP sends the error message directly to the user via STDOUT. In a command-line environment, this means that errors are rendered in the terminal. In a web environment, errors and exceptions get displayed directly in the browser.
While this behavior is useful for debugging problems in a development environment, it should be disabled in a production environment for security reasons. To do this, open up the PHP configuration file for the environment you are working in—typically found in a path that looks like /etc/php/:environment:/php.ini—and change the display_errors directive to Off.
While rendering errors to STDOUT is great for debugging issues in a development environment as they happen, it isn't very useful in a production environment. This is where the error log comes into play. By default, PHP doesn't log any errors, which means that this value must be explicitly set. To do so, open up the same PHP configuration file referenced above in your favorite editor and find the error_log directive.
There are two possible values for error_log: a custom log file and the syslog. If the syslog is used, then all PHP errors will be sent directly to the default system log file—in Linux, this is typically /var/log/syslog. The more manageable method is to use a custom log file. By doing this, you can isolate your PHP application's logs from the rest of the system logs, which can make debugging issues significantly easier.
Logging in Laravel
While PHP's default system logger is useful for bespoke applications, it is important to note that many application frameworks provide their own built-in logging mechanisms. A great example of this is the Laravel framework. In Laravel, the logging method can be changed within the log option of the application configuration file—found in config/app.php.
By default, Laravel maintains a single log file at storage/logs/laravel.log within the project directory, rather than the defined error_log option from the global PHP configuration.
Logging in Symfony
Because Laravel is built on top of Symfony, they share the same core logging mechanism—although the configuration differs between the two frameworks. Logging in Symfony and Laravel are both done using Monolog, a third-party PHP logging library that can be used to create and store logs in a large number of ways.
By default, Symfony logs are stored in var/log/dev.log and var/log/prod.log within the project directory, depending on the environment, but these defaults can be changed in the Monolog package configuration file found at config/packages/monolog.php.
What do PHP logs look like?
So, what exactly do PHP logs look like? In most instances, PHP logs follow a fairly predictable format:
In a nutshell, the log line above can be broken up into four parts: the date, the hostname, the process, and the error message. Whenever an error is encountered or an uncaught exception is thrown, the error message is printed along with the date, hostname, and process metadata to help pinpoint what happened, where it happened, and when it happened.
A primer on log levels
It is important to note that, in PHP, there are a handful of log levels that can be squashed or raised. While these log levels are determined by PHP itself, understanding what they are and mean is a crucial step towards being able to diagnose problems as they happen.
When display_errors is set to On, it can be useful to explicitly hide and show specific log levels so you can focus on one task at a time, such as critical errors, or cleaning up warnings. This can be accomplished using the built-in error_reporting method.
This method accepts an integer value that tells PHP which errors to display, and which ones to ignore. Through the use of bitwise operators (| meaning OR, & meaning AND, and ~ meaning NOT), we can clearly and easily define which errors we want to see.
Here are a few of the most common log levels. For more information about log levels (there are quite a few of them), take a look at PHP's official documentation.
How do I log errors in PHP?
To log errors in PHP, open the php. ini file and uncomment/add the following lines of code. If you want to enable PHP error logging in individual files, add this code at the top of the PHP file. ini_set('display_errors', 1); ini_set('display_startup_errors', 1); error_reporting(E_ALL);
How do you create an error log?
6 Ways To Make Error Logs Your New Secret Weapon.
Don't treat all errors the same. ... .
Make sure each error log provides context. ... .
Monitor frequency next to the context. ... .
Make error log history easy to search. ... .
Critical Errors need real time alerts. ... .
Use the right channel to monitor error logs..
How do I enable PHP logging?
To enable error logging for your site or application, follow these steps:.
Locate the php. ini file on your server..
Look for the line containing the error_reporting entry..
Ensure there is not a semicolon (;) in front of the entry..
Set the error_reporting entry equal to the desired level of logging (covered next)..
What is Errorlog file?
An error log is a file that contains detailed records of error conditions a computer software encounters when it's running. The name is generic: sometimes, an application can log non-error type messages in its error log. However, error logs are generally meant to record only error messages generated by a program.