custom-nextpage-fix-permalink.diff

Index: custom-nextpage.php
===================================================================
--- custom-nextpage.php	(revision 1388038)
+++ custom-nextpage.php	(working copy)
@@ -142,7 +142,7 @@
 	}
 
 	public function wp_link_pages( $output = '' ) {
-		global $page, $numpages, $multipage, $pagenow;
+		global $wp_query, $wp_rewrite, $page, $numpages, $multipage, $pagenow;
 		$output = '';
 		if ( $multipage ) {
 			$show_all         = (boolean) $this->show_all;
@@ -171,18 +171,25 @@
 					$output .= '<li class="previous">' . $link . $previouspagelink . '</a></li>';
 			}
 
-			$p_base   = get_permalink();
-			$p_format = '%#%';
+	    // Setting up default values based on the current URL.
+	    $pagenum_link = html_entity_decode( get_pagenum_link() );
+	    $url_parts    = explode( '?', $pagenum_link );
 
-			if($word = strpos($p_base, '?')){
-				$p_base = get_option(home).(substr(get_option(home), -1 ,1) === '/' ? '' : '/')
-					.'%_%'.substr($p_base, $word);
-			} else{
-				$p_base .= (substr($p_base, -1 ,1) === '/' ? '' : '/') .'%_%';
-			}
+	    // Get max pages and current page out of the current query, if available.
+	    $total   = isset( $wp_query->max_num_pages ) ? $wp_query->max_num_pages : 1;
+	    $current = get_query_var( 'page' ) ? intval( get_query_var( 'page' ) ) : 1;
+
+	    // Append the format placeholder to the base URL.
+	    $pagenum_link = trailingslashit( $url_parts[0] ) . '%_%';
+
+	    // URL base depends on permalink settings.
+	    $format  = $wp_rewrite->using_index_permalinks() && ! strpos( $pagenum_link, 'index.php' ) ? 'index.php/' : '';
+	    $format .= $wp_rewrite->using_permalinks() ? user_trailingslashit( $wp_rewrite->pagination_base . '/%#%', 'page' ) : '?page=%#%';
+
+
 			$nav_list = paginate_links(array(
-				'base'      => $p_base,
-				'format'    => $p_format,
+				'base' => $pagenum_link, // http://example.com/all_posts.php%_% : %_% is replaced by format (below)
+        'format' => $format, // ?page=%#% : %#% is replaced by the page number
 				'total'     => $numpages,
 				'current'   => ($page ? $page : 1),
 				'show_all'  => $show_all,