[PHP] How to get a function backtrace?

[Stefan Rusterholz]

Im not sure if "function-backtrace" is the correct word for what I need, so I'll 
explain:
If I have for example

<?
    a();
    function a(){
        b();
    }

    function b(){
        c();
    }

    function c(){
        $x = function_backtrace();
        print_r($x);
    }
?>

then I want to get

array(
    [0]    => 'a',
    [1]    => 'b',
    [2]    => 'c'
)

or something similar. So I want to know, what functions have been called. If you know 
perl, then adequate function was "caller".
I already searched php.net for it but had no luck for it - so if you please could 
point me to the right direction I was very happy.

TIA
Stefan Rusterholz