<?PHP 

echo "<a href='index.PHP?choice=search&cat=".$cat."&subcat=".$subcat."&srch=".$srch."&page=".$next."'> Next </a>";

?>

echo "<a href='index.PHP?choice=search&cat=".urlencode($cat)."&subcat=".urlencode($subcat)."&srch=".urlencode($srch)."&page=".urlencode($next)."'> Next </a>";