problem mit next_post_link / preview_post_link und exclude

function get_previous_post($in_same_cat = false, $excluded_categories = '') {
	global $post, $wpdb;


	if( !is_single() || is_attachment() )
		return null;


	$current_post_date = $post->post_date;


	$join = '';
	if ( $in_same_cat ) {
		$join = " INNER JOIN $wpdb->post2cat ON $wpdb->posts.ID= $wpdb->post2cat.post_id ";
		$cat_array = get_the_category($post->ID);
		$join .= ' AND (category_id = ' . intval($cat_array[0]->cat_ID);
		for ( $i = 1; $i < (count($cat_array)); $i++ ) {
			$join .= ' OR category_id = ' . intval($cat_array[$i]->cat_ID);
		}
		$join .= ')'; 
	}


	$sql_exclude_cats = '';
	if ( !empty($excluded_categories) ) {
		/*
		$blah = explode('and', $excluded_categories);
		foreach ( $blah as $category ) {
			$category = intval($category);
			$sql_exclude_cats .= " AND post_category != $category";
		}*/
		# Modified by bjoern klein #
		$exclude = explode('and',$excluded_categories);
		$tmp = " INNER JOIN $wpdb->post2cat ON ($wpdb->posts.ID = $wpdb->post2cat.post_id AND NOT (category_id IN (".implode(',',$exclude)."))) ";
		$join .= $tmp;
	}


	return @$wpdb->get_row("SELECT ID, post_title FROM $wpdb->posts $join WHERE post_date < '$current_post_date' AND post_status = 'publish' $sqlcat $sql_exclude_cats ORDER BY post_date DESC LIMIT 1");
}


function get_next_post($in_same_cat = false, $excluded_categories = '') {
	global $post, $wpdb;


	if( !is_single() || is_attachment() )
		return null;


	$current_post_date = $post->post_date;
	
	$join = '';
	if ( $in_same_cat ) {
		$join = " INNER JOIN $wpdb->post2cat ON $wpdb->posts.ID= $wpdb->post2cat.post_id ";
		$cat_array = get_the_category($post->ID);
		$join .= ' AND (category_id = ' . intval($cat_array[0]->cat_ID);
		for ( $i = 1; $i < (count($cat_array)); $i++ ) {
			$join .= ' OR category_id = ' . intval($cat_array[$i]->cat_ID);
		}
		$join .= ')'; 
	}


	$sql_exclude_cats = '';
	if ( !empty($excluded_categories) ) {
		/*$blah = explode('and', $excluded_categories);
		foreach ( $blah as $category ) {
			$category = intval($category);
			$sql_exclude_cats .= " AND post_category != $category";
		}*/
		
		# Modified by bjoern klein #
		$exclude = explode('and',$excluded_categories);
		$tmp = " INNER JOIN $wpdb->post2cat ON ($wpdb->posts.ID = $wpdb->post2cat.post_id AND NOT (category_id IN (".implode(',',$exclude)."))) ";
		$join .= $tmp;
	}


	$now = current_time('mysql');
	
	return @$wpdb->get_row("SELECT ID,post_title FROM $wpdb->posts $join WHERE post_date > '$current_post_date' AND post_date < '$now' AND post_status = 'publish' $sqlcat $sql_exclude_cats AND ID != $post->ID ORDER BY post_date ASC LIMIT 1");
}