I shouldn't've posted the original version, as it only worked with the most basic of query strings.
This function will parse an html-safe query-like url string for variables and php-like ordered and associative arrays. It places them into the global scope as parse_str does and adds minimal slashes for database insertions without the triple-slash problems that magic quotes can produce (the reason I had to write it in the first place). If you don't need the slashes, they're easy enough to remove.
<?php
function parse_query($str) {
 
 // Separate all name-value pairs
 $pairs = explode('&', $str);
 
 foreach($pairs as $pair) {
 
 // Pull out the names and the values
 list($name, $value) = explode('=', $pair, 2);
 
 // Decode the variable name and look for arrays
 list($name, $index) = split('[][]', urldecode($name));
 
 // Arrays
 if(isset($index)) {
 
 // Declare or add to the global array defined by $name
 global $$name;
 if(!isset($$name)) $$name = array();
 
 // Associative array
 if($index != "") {
 ${$name}[$index] = addslashes(urldecode($value));
 
 // Ordered array
 } else {
 array_push($$name, addslashes(urldecode($value)));
 }
 
 // Variables
 } else {
 
 // Declare or overwrite the global variable defined by $name
 global $$name;
 $$name = addslashes(urldecode($value));
 }
 }
}
?>