How to log error message in drupal - php

Question

How to log our own error messages(for ex: error due to invalid user date entry) which is generated in php program to drupal error log.

Answer 1

You can use the watchdog function :
watchdog($type, $message, $variables = array(), $severity = WATCHDOG_NOTICE, $link = NULL)
Quoting the manual, the parameters are :
$type The category to which this message belongs.
$message The message to store in the log.
$variables Array of variables to replace in the message on display or NULL if message is already translated or not possible to translate.
$severity The severity of the message, as per RFC 3164
$link A link to associate with the message.
And the error levels can be found on the page of watchdog_severity_levels. For an error, you'll most probably use WATCHDOG_ERROR, or maybe even something more "critical", depending on the kind of error.

Answer 2

Drupal 8+
// Logs a notice
\Drupal::logger('my_module')->notice($message);
// Logs an error
\Drupal::logger('my_module')->error($message);
See more examples at How to Log Messages in Drupal 8.

Answer 3

1) Indeed, watchdog is a standard way to record own PHP errors.
2) Alternatively, if you need to immediately see error messages while debugging your Drupal pages, you may want to see them logged/printed right at the related page - in FireBug console.
Sometimes is this very convenient when you can see page-related just-in-time logs.
This requires - Devel module, Firebug extension to FireFox and possibly Firephp.
You can use the dfb() function to write log messages directly to the general Firebug console.
dfb($input, $label = NULL)
If you want to keep your Drupal-related log messages out of the normal Firebug console, you can write messages to the Drupal for Firebug log with the firep() function:
firep($item, $optional_title)

Answer 4

Watchdog is the way to go for a production system no doubt but during debugging I find the drupal_set_message function useful.
It outputs the message to the screen where the 'Operation Successful'-type messages are normally displayed (so make sure you remove them before making the site Live).
http://api.drupal.org/api/function/drupal_set_message/6

Answer 5

In drupal 7 we can log message by following method:
drupal watchdog function we can use to log message in database , make sure we have enabled optional core module for Database Logging at /admin/build/modules.
watchdog($type, $message, $variables = array(), $severity = WATCHDOG_NOTICE, $link = NULL)
$type:
The category to which this message belongs , Example: PHP,cron.., we can filter message by type.
$message :
The message to store in the log,Example: 'The following module is missing from the file system: security_review'
$variables :
Array of variables to replace in the message on display or NULL if message is already translated or not possible to translate.
to make message translated , do not pass dynamic value pass variables in the message should be added by using placeholder strings.
Example:
watchdog('cg_volunteer', 'cg in form_alter %formly', array('%formly' => $form['#id']), WATCHDOG_NOTICE, $link = NULL);
$severity
The severity of the message,logs can be filter by severity as per RFC 3164. Possible values are WATCHDOG_ERROR, WATCHDOG_WARNING, etc.
For more example see https://api.drupal.org/api/drupal/includes!bootstrap.inc/function/watchdog/7.x
$link:
A link to associate with the message.
Example
// for logs notices
watchdog('my_module', $message, array());
// for Loging Error
watchdog('my_module', $message, array(), WATCHDOG_ERROR);
In drupal 8 we used following method:
// For Logs a notice.
\Drupal::logger('my_module')->notice($message);
// For Logs an error.
\Drupal::logger('my_module')->error($message);
// For Alert, action must be taken immediately.
\Drupal::logger('my_module')->alert($message);
// For Critical message.
\Drupal::logger('my_module')->critical($message);
// For Debug-level messages.
\Drupal::logger('my_module')->debug($message);
//For Emergency, system is unusable.
\Drupal::logger('my_module')->emergency($message);
//For Warning
\Drupal::logger('my_module')->warning($message);
//For Informational messages.
\Drupal::logger('my_module')->info($message);
Also for translate we should not use t() function.
\Drupal::logger('my_module')->alert('Message from #module: #message.', [
'#module' => $module,
'#message' => $message,
]);
this will be translated on run time.
Example :
\Drupal::logger('content_entity_example')->notice('#type: deleted %title.',
array(
'#type' => $this->entity->bundle(),
'%title' => $this->entity->label(),
));

Answer 6

Both watchdog for D7 & \Drupal::logger for D8 will write log in watchdog table (in your database), and with HUGE data logged, you can imagine performance impact.
You can use error_log php function to do it (see PHP manual).
error_log("Your message", 3, "/path/to/your/log/file.log");
You need to have permission to write in your log file (/path/to/your/log/file.log)
drupal-8drupalphplog

Answer 7

// Get logger factory.
$logger = \Drupal::service('logger.factory');
// Log a message with dynamic variables.
$nodeType = 'Article';
$userName = 'Admin';
$logger->get($moduleName)->notice('A new "#nodeType" created by %userName.', [
'#nodeType' => $nodeType,
'%userName' => $userName,
]);
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