http_build_url_PHP

<?php
    if (!function_exists('http_build_url'))
    {
        define('HTTP_URL_REPLACE', 1);              // Replace every part of the first URL when there's one of the second URL
        define('HTTP_URL_JOIN_PATH', 2);            // Join relative paths
        define('HTTP_URL_JOIN_QUERY', 4);           // Join query strings
        define('HTTP_URL_STRIP_USER', 8);           // Strip any user authentication information
        define('HTTP_URL_STRIP_PASS', 16);          // Strip any password authentication information
        define('HTTP_URL_STRIP_AUTH', 32);          // Strip any authentication information
        define('HTTP_URL_STRIP_PORT', 64);          // Strip explicit port numbers
        define('HTTP_URL_STRIP_PATH', 128);         // Strip complete path
        define('HTTP_URL_STRIP_QUERY', 256);        // Strip query string
        define('HTTP_URL_STRIP_FRAGMENT', 512);     // Strip any fragments (#identifier)
        define('HTTP_URL_STRIP_ALL', 1024);         // Strip anything but scheme and host

        // Build an URL
        // The parts of the second URL will be merged into the first according to the flags argument.
        //
        // @param   mixed           (Part(s) of) an URL in form of a string or associative array like parse_url() returns
        // @param   mixed           Same as the first argument
        // @param   int             A bitmask of binary or'ed HTTP_URL constants (Optional)HTTP_URL_REPLACE is the default
        // @param   array           If set, it will be filled with the parts of the composed url like parse_url() would return
        function http_build_url($url, $parts=array(), $flags=HTTP_URL_REPLACE, &$new_url=false)
        {
            $keys = array('user','pass','port','path','query','fragment');

            // HTTP_URL_STRIP_ALL becomes all the HTTP_URL_STRIP_Xs
            if ($flags & HTTP_URL_STRIP_ALL)
            {
                $flags |= HTTP_URL_STRIP_USER;
                $flags |= HTTP_URL_STRIP_PASS;
                $flags |= HTTP_URL_STRIP_PORT;
                $flags |= HTTP_URL_STRIP_PATH;
                $flags |= HTTP_URL_STRIP_QUERY;
                $flags |= HTTP_URL_STRIP_FRAGMENT;
            }
            // HTTP_URL_STRIP_AUTH becomes HTTP_URL_STRIP_USER and HTTP_URL_STRIP_PASS
            else if ($flags & HTTP_URL_STRIP_AUTH)
            {
                $flags |= HTTP_URL_STRIP_USER;
                $flags |= HTTP_URL_STRIP_PASS;
            }

            // Parse the original URL
            $parse_url = parse_url($url);

            // Scheme and Host are always replaced
            if (isset($parts['scheme']))
                $parse_url['scheme'] = $parts['scheme'];
            if (isset($parts['host']))
                $parse_url['host'] = $parts['host'];

            // (If applicable) Replace the original URL with it's new parts
            if ($flags & HTTP_URL_REPLACE)
            {
                foreach ($keys as $key)
                {
                    if (isset($parts[$key]))
                        $parse_url[$key] = $parts[$key];
                }
            }
            else
            {
                // Join the original URL path with the new path
                if (isset($parts['path']) && ($flags & HTTP_URL_JOIN_PATH))
                {
                    if (isset($parse_url['path']))
                        $parse_url['path'] = rtrim(str_replace(basename($parse_url['path']), '', $parse_url['path']), '/') . '/' . ltrim($parts['path'], '/');
                    else
                        $parse_url['path'] = $parts['path'];
                }

                // Join the original query string with the new query string
                if (isset($parts['query']) && ($flags & HTTP_URL_JOIN_QUERY))
                {
                    if (isset($parse_url['query']))
                        $parse_url['query'] .= '&' . $parts['query'];
                    else
                        $parse_url['query'] = $parts['query'];
                }
            }

            // Strips all the applicable sections of the URL
            // Note: Scheme and Host are never stripped
            foreach ($keys as $key)
            {
                if ($flags & (int)constant('HTTP_URL_STRIP_' . strtoupper($key)))
                    unset($parse_url[$key]);
            }


            $new_url = $parse_url;

            return
                 ((isset($parse_url['scheme'])) ? $parse_url['scheme'] . '://' : '')
                .((isset($parse_url['user'])) ? $parse_url['user'] . ((isset($parse_url['pass'])) ? ':' . $parse_url['pass'] : '') .'@' : '')
                .((isset($parse_url['host'])) ? $parse_url['host'] : '')
                .((isset($parse_url['port'])) ? ':' . $parse_url['port'] : '')
                .((isset($parse_url['path'])) ? $parse_url['path'] : '')
                .((isset($parse_url['query'])) ? '?' . $parse_url['query'] : '')
                .((isset($parse_url['fragment'])) ? '#' . $parse_url['fragment'] : '')
            ;
        }
    }