if you need custom arg separator, you can use this function. it returns parsed  query as associative array.

<?php

/**
 * Parses http query string into an array
 * 
 * @author Alxcube <alxcube@gmail.com>
 * 
 * @param string $queryString String to parse
 * @param string $argSeparator Query arguments separator
 * @param integer $decType Decoding type
 * @return array
 */
function http_parse_query($queryString, $argSeparator = '&', $decType = PHP_QUERY_RFC1738) {
        $result             = array();
        $parts              = explode($argSeparator, $queryString);

        foreach ($parts as $part) {
                list($paramName, $paramValue)   = explode('=', $part, 2);

                switch ($decType) {
                        case PHP_QUERY_RFC3986:
                                $paramName      = rawurldecode($paramName);
                                $paramValue     = rawurldecode($paramValue);
                                break;

                        case PHP_QUERY_RFC1738:
                        default:
                                $paramName      = urldecode($paramName);
                                $paramValue     = urldecode($paramValue);
                                break;
                }
                

                if (preg_match_all('/\[([^\]]*)\]/m', $paramName, $matches)) {
                        $paramName      = substr($paramName, 0, strpos($paramName, '['));
                        $keys           = array_merge(array($paramName), $matches[1]);
                } else {
                        $keys           = array($paramName);
                }
                
                $target         = &$result;
                
                foreach ($keys as $index) {
                        if ($index === '') {
                                if (isset($target)) {
                                        if (is_array($target)) {
                                                $intKeys        = array_filter(array_keys($target), 'is_int');
                                                $index  = count($intKeys) ? max($intKeys)+1 : 0;
                                        } else {
                                                $target = array($target);
                                                $index  = 1;
                                        }
                                } else {
                                        $target         = array();
                                        $index          = 0;
                                }
                        } elseif (isset($target[$index]) && !is_array($target[$index])) {
                                $target[$index] = array($target[$index]);
                        }

                        $target         = &$target[$index];
                }

                if (is_array($target)) {
                        $target[]   = $paramValue;
                } else {
                        $target     = $paramValue;
                }
        }

        return $result;
}

?>