Finding out the filename that called my function in PHP

Try this code:

$key = array_search(__FUNCTION__, array_column(debug_backtrace(), 'function'));
var_dump(debug_backtrace()[$key]['file']);

A solution might be to use the debug_backtrace function : in the backtrace, that kind of information should be present.

Or, as Gordon pointed out in a comment, you can also use debug_print_backtrace if you just want to output that information and not work with it.

For instance, with temp.php containing this :

<?php
include 'temp-2.php';
my_function();

and with temp-2.php containing this :

<?php
function my_function() {
    var_dump(debug_backtrace());
}

Calling temp.php (i.e. the first script) from my browser gets me this output :

array
  0 => 
    array
      'file' => string '/.../temp/temp.php' (length=46)
      'line' => int 5
      'function' => string 'my_function' (length=11)
      'args' => 
        array
          empty

In there, I have the "temp.php" filename -- which is the one in which the function has been called.

Of course, you'll have to test a bit more (especially in situations where the function is not in the "first level" included file, but in a file included by another one -- not sure debug_backtrace will help much, there...) ; but this might help you get a first idea...