1  function link_back($blacklist = array())
   2  	{
   3  		$parameters = split("&", $_SERVER['QUERY_STRING']);
   4  		
   5  		$uri = array_shift(split("\?", $_SERVER['REQUEST_URI']));
   6  
   7  		$index = 0;
   8  		
   9  		foreach($parameters as $parameter)
  10  		{
  11  			$parameter = split("=", $parameter);
  12  			
  13  			$name = $parameter[0];
  14  			$value = $parameter[1];
  15  			
  16  			if(in_array($name, $blacklist))
  17  			{
  18  				unset($parameters[$index]);
  19  			}
  20  			
  21  			$index++;
  22  		}
  23  		
  24  		if(count($parameters) > 0)
  25  		{
  26  			$parameters = "?".join("&", $parameters);	
  27  		}
  28  		else
  29  		{
  30  			$parameters = '';
  31  		}
  32  		
  33  		return $uri.$parameters;
  34  	}

Usage:

   1  # URI is /wow_amazing_code?not_wanted=23&wanted=1
   2  
   3  echo link_back(array('not_wanted')); # prints out /wow_amazing_code?wanted=1