Someone

for($p=1 ; $p<$nbpage+1 ; $p++){
				if($p=$page){
					echo'<span class="lienpage_actif"><a href="forum.php?cat='.$_GET['cat'].'?page='.$p.'" title="">'.$p.'</a> </span>';
				}else{
					echo'<span class="lienpage"><a href="forum.php?cat='.$_GET['cat'].'?page='.$p.'" title="">'.$p.'</a> </span>';
				}
			}