function-stringify.php

<?php                                                                           
function function_stringify($func) {                                                      

    $ref = new ReflectionFunction($func);                                       

    if ($ref->isInternal())                                                     
        return '[internal]';                                                    

    $top = $ref->getStartLine() - 1;                                            
    $len = $ref->getEndLine() - $top;                                           
    $src = implode('', array_slice(file($ref->getFilename()), $top, $len));     

    return $src;                                                                
}