Simple static library that allows easy manipulation of url parameters:

<?php
    /**
     * File provides easy way to manipulate url parameters
     * @author Alexander Podgorny
     */

    class Url {
        /**
         * Splits url into array of it's pieces as follows:
         * [scheme]://[user]:[pass]@[host]/[path]?[query]#[fragment]
         * In addition it adds 'query_params' key which contains array of 
         * url-decoded key-value pairs
         *
         * @param String $sUrl Url
         * @return Array Parsed url pieces
         */
        public static function explode($sUrl) {
            $aUrl = parse_url($sUrl);
            $aUrl['query_params'] = array();
            $aPairs = explode('&', $aUrl['query']);
            DU::show($aPairs);
            foreach($aPairs as $sPair) {
                if (trim($sPair) == '') { continue; }
                list($sKey, $sValue) = explode('=', $sPair);
                $aUrl['query_params'][$sKey] = urldecode($sValue);
            }
            return $aUrl;
        }
        /**
         * Compiles url out of array of it's pieces (returned by explodeUrl)
         * 'query' is ignored if 'query_params' is present
         * 
         * @param Array $aUrl Array of url pieces
         */
        public static function implode($aUrl) {
            //[scheme]://[user]:[pass]@[host]/[path]?[query]#[fragment]
            
            $sQuery = '';
            
            // Compile query
            if (isset($aUrl['query_params']) && is_array($aUrl['query_params'])) {
                $aPairs = array();
                foreach ($aUrl['query_params'] as $sKey=>$sValue) {
                    $aPairs[] = $sKey.'='.urlencode($sValue);               
                }
                $sQuery = implode('&', $aPairs);    
            } else {
                $sQuery = $aUrl['query'];
            }
            
            // Compile url
            $sUrl = 
                $aUrl['scheme'] . '://' . (
                    isset($aUrl['user']) && $aUrl['user'] != '' && isset($aUrl['pass']) 
                       ? $aUrl['user'] . ':' . $aUrl['pass'] . '@' 
                       : ''
                ) .
                $aUrl['host'] . (
                    isset($aUrl['path']) && $aUrl['path'] != ''
                       ? $aUrl['path']
                       : ''
                ) . (
                   $sQuery != ''
                       ? '?' . $sQuery
                       : ''
                ) . (
                   isset($aUrl['fragment']) && $aUrl['fragment'] != ''
                       ? '#' . $aUrl['fragment']
                       : ''
                );
            return $sUrl;
        }
        /**
         * Parses url and returns array of key-value pairs of url params
         *
         * @param String $sUrl
         * @return Array
         */
        public static function getParams($sUrl) {
            $aUrl = self::explode($sUrl);
            return $aUrl['query_params'];
        }
        /**
         * Removes existing url params and sets them to those specified in $aParams
         *
         * @param String $sUrl Url
         * @param Array $aParams Array of Key-Value pairs to set url params to
         * @return  String Newly compiled url 
         */
        public static function setParams($sUrl, $aParams) {
            $aUrl = self::explode($sUrl);
            $aUrl['query'] = '';
            $aUrl['query_params'] = $aParams;
            return self::implode($aUrl);
        }
        /**
         * Updates values of existing url params and/or adds (if not set) those specified in $aParams
         *
         * @param String $sUrl Url
         * @param Array $aParams Array of Key-Value pairs to set url params to
         * @return  String Newly compiled url 
         */
        public static function updateParams($sUrl, $aParams) {
            $aUrl = self::explode($sUrl);
            $aUrl['query'] = '';
            $aUrl['query_params'] = array_merge($aUrl['query_params'], $aParams);
            return self::implode($aUrl);
        }
    }

?>