If you need a function that does something similar to parse_str, but doesn't convert spaces and dots to underscores, try something like the following:

<?php
function parseQueryString($str) {
    $op = array();
    $pairs = explode("&", $str);
    foreach ($pairs as $pair) {
        list($k, $v) = array_map("urldecode", explode("=", $pair));
        $op[$k] = $v;
    }
    return $op;
}
?>

It may need adapting to handle various edge cases.