@mad_max
finally it work ! special thanks but I modified a little bit :
if ( isset( $query_string['cat'] ) ) {
switch ($query_string['cat']) {
case 1:
$query_string['posts_per_page'] = 2;
break;
case 5:
$query_string['posts_per_page'] = 8;
break;
case 3:
$query_string['posts_per_page'] = 6;
// default:
// $query_string['posts_per_page'] = 6;
break;
}
}
because WP don’t recognize ‘category_name’, maybe because I don’t use permalinks with localhost.
THX