PHP determines if there are certain items in the URL parameter

<?PHP$old _url=$_server["Request_uri"];//Check to see if the link exists?$check=Strpos($old _url, ‘?‘);//if it exists?if($check!==false){//What if there are no parameters, such as http://www.yitu.org/index.php?if(substr($old _url,$check+1) = = "'){//additional parameters can be added directly$new _url=$old _url;}Else //If there are parameters, such as: Http://www.yitu.org/index.php?ID=12{$new _url=$old _url.‘ & ';}}Else //What if it doesn't exist?{$new _url=$old _url.‘?‘;}Echo $new _url;?>