How to output PHP code when the runtime calls the class, that method

How does the output PHP code run when called the class, that method?
For example: Starting from the entry file, until the end of an operation, the use of what classes, which methods and so on.
1. It starts with a portal file, which classes, which methods, and how to obtain them are used during the run. Is there a method or function to get this information?
2. Because some packages are too large, too many branches, bad analysis took that step, if you can get this information can quickly analyze the code flow?
Thank you, you are a novice! So find the class, find a way, a little slow, want to ask this kind of method.

------Solution--------------------
What frame does the landlord use? CI is configured:
config/config.php
$config [' log_threshold '] = 2;
You can see all the debugging information.

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