Blackfire is a tool that allows you to profile your PHP applications.
You can use it for PHP scripts (like Symfony Commands) or for HTTP requests in your browser or via cURL. Blackfire provides detailed insights into the execution of your code, identifying bottlenecks and monitoring memory usage.
If you encounter any performance issues in your code, Blackfire is the most powerful tool to identify the root causes.
This means you must use the Symfony CLI command symfony to execute PHP scripts (e.g., symfony php ./my-script.php) or a Symfony command (symfony console app:my-command), depending on what you want to profile and how.