better way to replace query string value in a given url

Well, I had same problem, found this question, and, in the end, prefered my own method. Maybe it has flaws, then please tell me what are they. My solution is:

$query=$_GET;
$query['YOUR_NAME']=$YOUR_VAL;
$url=$_SERVER['PHP_SELF']. '?' .  http_build_query($query);

Hope it helps.

How about something like this?

function merge_querystring($url = null,$query = null,$recursive = false)
{
  // $url = 'http://www.google.com.au?q=apple&type=keyword';
  // $query = '?q=banana';
  // if there's a URL missing or no query string, return
  if($url == null)
    return false;
  if($query == null)
    return $url;
  // split the url into it's components
  $url_components = parse_url($url);
  // if we have the query string but no query on the original url
  // just return the URL + query string
  if(empty($url_components['query']))
    return $url.'?'.ltrim($query,'?');
  // turn the url's query string into an array
  parse_str($url_components['query'],$original_query_string);
  // turn the query string into an array
  parse_str(parse_url($query,PHP_URL_QUERY),$merged_query_string);
  // merge the query string
  if($recursive == true)
    $merged_result = array_merge_recursive($original_query_string,$merged_query_string);
  else
    $merged_result = array_merge($original_query_string,$merged_query_string);
  // Find the original query string in the URL and replace it with the new one
  return str_replace($url_components['query'],http_build_query($merged_result),$url);
}

usage...

<a href="<?=merge_querystring($url,'?page=1');?>">Page 1</a>
<a href="<?=merge_querystring($url,'?page=2');?>">Page 2</a>