How does PHP determine what target called it in a method?

Question

1. Just like the title
2. Code

a.php

include(b.php);
b();

b.php

function b(){

   echo 'What calls me is the second line of a.php';
}

The code is as above. How can we determine who called it in b and get the file name and line number

Answer 1

debug_backtrace()