Enhanced Sorting by Nested Meta Values in Pages (#681)

* Added functionality for sorting pages by nested meta values.

* Additional variables removed.

* Added comment to the config template file about the possibility to access nested metadata with a dot as separator for sorting.

* Added entry in the changelog about the possibility to access nested metadata with a dot as separator for sorting.

* Changelog and config template adapted according to the suggestions.

* Added old entry back in the Config template.

CHANGELOG.md

@@ -32,6 +32,8 @@ Released: -
         now receive the (optional) `$pageId` argument for the new `%page_*%`
         Markdown placeholders
 * [New] Add `page()` Twig function to access a page's data
+* [New] Enhance `pages_order_by_meta` functionality to allow sorting by 
+            nested meta values using '.' notation (e.g., 'author.info')
 * [Changed] ! Pico now requires PHP 7.2.5 or later (this includes full PHP 8
             support, also see #528, #534, #608)
 * [Changed] ! Pico now depends on Twig 3.3, skipping Twig 2.x altogether; this

config/config.yml.template

@@ -31,6 +31,7 @@ twig_config:                        # Twig template engine config
 date_format: "%D %T"                # Pico's default date format;
                                     #     See https://php.net/manual/en/function.strftime.php for more info
 pages_order_by_meta: author         # Sort pages by meta value "author" (set "pages_order_by" to "meta")
+                                    #     Use '.' notation for nested meta keys (e.g. 'author.info')
 pages_order_by: alpha               # Change how Pico sorts pages ("alpha" for alphabetical order, "date", or "meta")
 pages_order: asc                    # Sort pages in ascending ("asc") or descending ("desc") order
 content_dir: ~                      # The path to Pico's content directory

lib/Pico.php

@@ -1877,11 +1877,18 @@ class Pico
         if ($orderBy === 'meta') {
             // sort by arbitrary meta value
             $orderByMeta = $this->getConfig('pages_order_by_meta');
-            uasort($this->pages, function ($a, $b) use ($alphaSortClosure, $order, $orderByMeta) {
+            $orderByMetaKeys = explode('.', $orderByMeta);
-                $aSortValue = isset($a['meta'][$orderByMeta]) ? $a['meta'][$orderByMeta] : null;
+
-                $aSortValueNull = ($aSortValue === null);
+            uasort($this->pages, function ($a, $b) use ($alphaSortClosure, $order, $orderByMetaKeys) {
+                $aSortValue = $a['meta'];
+                $bSortValue = $b['meta'];
                 
-                $bSortValue = isset($b['meta'][$orderByMeta]) ? $b['meta'][$orderByMeta] : null;
+                foreach ($orderByMetaKeys as $key) {
+                    $aSortValue = isset($aSortValue[$key]) ? $aSortValue[$key] : null;
+                    $bSortValue = isset($bSortValue[$key]) ? $bSortValue[$key] : null;
+                }
+
+                $aSortValueNull = ($aSortValue === null);
                 $bSortValueNull = ($bSortValue === null);
 
                 $cmp = 0;