Identify PHP Process by ID ? (issue with exec time out)

Hello to the great CI community ! 

Recently i had issues with some execution time out while working on image resizing/cropping function.
The PHP FPM logs : 

Code:

[03-Nov-2017 12:25:25] WARNING: [pool www] child 41319, script '/srv/data/web/vhosts/www.website.com/htdocs/index.php' (request: "GET /index.php") execution timed out (198.751251 sec), terminating
[03-Nov-2017 12:25:25] WARNING: [pool www] child 41319 exited on signal 15 (SIGTERM) after 229.774670 seconds from start

The only information i have to identify the guilty process PHP is the child number 41319

There is a way to have more informations about it ? I checked all the others logs and i found nothing. 
So maybe i need to create my own logs about that ? There is a way to do that using CI or a best method to use ?  
or a CI way to store any issues ? 

I saw on other people logs reference to "child 21597 stopped for tracing / about to trace 21597 / finished trace of 21597" but i don't know how to do that.

If you have some ideas about all of that, it will be a great help ! 
Thanks !