PHP debug_backtrace() stack debugging

<?php 
function one($str1, $str2) 
{ 
two("Glenn", "Quagmire"); 
} 
function
two($str1, $str2) 
{ 
three("Cleveland", "Brown"); 
} 
function three($str1,$str2) 
{ 
print_r(debug_backtrace()); 
} 
one("Peter", "Griffin"); 
?>

Array ( [0] => Array ( [file] => C:\webfolder\test.php [line] => 7
[function] => three [args] => Array ( [0] => Cleveland [1] => Brown ) )
[1] => Array ( [file] => C:\webfolder\test.php [line] => 3 [function] =>
two [args] => Array ( [0] => Glenn [1] => Quagmire ) ) [2] => Array (
[file] => C:\webfolder\test.php [line] => 14 [function] => one [args] =>
Array ( [0] => Peter [1] => Griffin ) ) )