trigger_error would not put anything to screen, it creates a myDebug log in the logs folder. If you wanted to have information in the superglobals plugin, then would need to capture data in a superglobal related variable. Just understand that what it reports is the "last" value that is held, not necessarily how the variable changes over time/execution.

Ie. If were to use $_SESSION['myVar'] = $myVarData; and that was within a loop, you would only see 1) whether the loop was executed the very first time that were looking at the superglobals plugin was active or if it was not executed, and 2) if it were executed what the value was at the last time it was executed....

This assumes also that the session variable was not unset at some point before it's first use or provided some other "default" value...

A lot of ways around this, but if determined to track information "uniquely" through such iterations, would suggest developing some sort of scheme that supports understanding the data seen. Ie. Using a counter within a loop where the number of times to loop is executed can be factored in, clearing such session variables before their use, ie. using a session variable that is an array where each element of the array provides a piece of data but the original session variable can be cleared by either unsetting the session variable or setting it to an empty array...

I hope that something from the above is understood, if not yet then probably will be more so after trying to actually store some value(s) to review...

As said, there are a lot of ways to collect data along the execution path.