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How to debug and filter the Apache error log by specified string (Linux)

Define how to display the Apache error log with a simple command

While you hunt a bug in your code you may wish to check the error log and refine the result. If you configured a virtual host you may use individual <site>-error.log and will be easier to track some errors. You may have problems with more than one live site on your machine.

But if you need to track the error log/debug by a specific string use this command in the console:

tail -f /var/log/apache2/error.log | grep --line-buffered my_string_here;

Example Usage

Let’s say we have a PHP script and want to log a message for debugging purposes:

<?php
// Log a simple message to the default error log
error_log("An error occurred in the application.");

// Log a variable value
$user_id = 123;
error_log("User ID: $user_id");

// Log to a specific file
error_log("Error: Something went wrong.", 3, "/var/www/logs/error.log");
?>

Benefits of Using error_log()

  • Convenience: error_log() provides a quick and easy way to log messages without the need for additional setup or external libraries.
  • Versatility: It allows logging to various destinations, including the default error log, specific files, or even sending emails.
  • Debugging: By strategically placing error_log() calls in the code, developers can track the flow of execution, inspect variable values, and identify potential issues.

Best Practices

  • Use Sparingly: While logging is essential for debugging, excessive logging can clutter the error log and impact performance. Log only the necessary information.
  • Secure Logging: Avoid logging sensitive information such as passwords or personal data to prevent security risks.
  • Monitor Logs: Regularly review error logs to catch and address any issues promptly.

By leveraging the error_log() function effectively, developers can streamline the debugging process and ensure the smooth functioning of PHP applications.

Important

Secure Logging: Avoid logging sensitive information such as passwords or personal data to prevent security risks.

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