Convert CamelCase to under_score_case in php __autoload()

Question

PHP manual suggests to autoload classes like

function __autoload($class_name){
 require_once(\"some_dir/\".$class_name.\".php\");
}

and this a

Answer 1

This is untested but I have used something similar before to convert the class name. I might add that my function also runs in O(n) and doesn't rely on slow backreferencing.

// lowercase first letter
$class_name[0] = strtolower($class_name[0]);

$len = strlen($class_name);
for ($i = 0; $i < $len; ++$i) {
    // see if we have an uppercase character and replace
    if (ord($class_name[$i]) > 64 && ord($class_name[$i]) < 91) {
        $class_name[$i] = '_' . strtolower($class_name[$i]);
        // increase length of class and position
        ++$len;
        ++$i;
    }
}

return $class_name;