Function in Python to PHP

Does anyone know how to convert this function from Python to PHP?

I have been around it but there is things in Python code I can't figure out.

This function is used in the follow context:
http://www.dmcloud.net/doc/api/general.html#authentication

def normalize(input=None):
output = ''

if type(input) in (list, tuple):
    for element in input:
        if type(element) in (dict, list, tuple):
            element = normalize(element)

        output += str(element)

elif type(input) is dict:
    keys = input.keys()
    keys.sort()
    for key in keys:
        element = input[key]
        if type(element) in (dict, list, tuple):
            element = normalize(element)
        output += '%s%s' % (key, element)


else:
    output = str(input)

return output

Thank you!

Answer

php has no distinction between dictionaries and tuples/lists, so:

function normalize($input=null) {
  if (! is_array($input)) {
    return strval($input);
  }

  $res = '';
  $keys = array_keys($input);
  sort($keys);
  foreach ($keys as $k) {

    if (!is_int($k)) $res .= $k;
    $res .= normalize($v);
  }
  return $res;
}

Notably, this serialization sucks, since it cannot distinguish integers from numbers. YOu should really be using JSON (in php as well as Python), which is a language-independent, human-readable serialization format.

Instead of using this string for authentication, one should simply use a hash over the JSON serialization.