Fixes #2906. Added elgg_sql_reverse_order_by() and wired it up to ege() and ega(). Pass 'reverse_order_by' => true in option arrays.

git-svn-id: http://code.elgg.org/elgg/trunk@8184 36083f99-b078-4883-b0ff-0f9b5a30f544

2 files changed, 33 insertions, 0 deletions

diff --git a/engine/lib/elgglib.php b/engine/lib/elgglib.php
index 12560308e..7ebf918b7 100644
--- a/engine/lib/elgglib.php
+++ b/engine/lib/elgglib.php
@@ -1659,6 +1659,30 @@ function css_page_handler($page) {
 }
 
 /**
+ * Reverses the ordering in an ORDER BY clause.  This is achived by replacing
+ * asc with desc, or appending desc to the end of the clause.
+ *
+ * This is used mostly for elgg_get_entities() and other similar functions.
+ *
+ * @access private
+ * @param string $order_by An order by clause
+ */
+function elgg_sql_reverse_order_by_clause($order_by) {
+	$order_by = strtolower($order_by);
+
+	if (strpos($order_by, ' asc') !== false) {
+		$return = str_replace(' asc', ' desc', $order_by);
+	} elseif (strpos($order_by, ' desc') !== false) {
+		$return = str_replace(' desc', ' asc', $order_by);
+	} else {
+		// no order specified, so default to desc since mysql defaults to asc
+		$return = $order_by . ' desc';
+	}
+
+	return $return;
+}
+
+/**
  * Intercepts the index page when Walled Garden mode is enabled.
  *
  * @link http://docs.elgg.org/Tutorials/WalledGarden
diff --git a/engine/lib/entities.php b/engine/lib/entities.php
index 4a1e496ec..7ab25de88 100644
--- a/engine/lib/entities.php
+++ b/engine/lib/entities.php
@@ -708,6 +708,8 @@ function get_entity($guid) {
  *
  * 	order_by => NULL (time_created desc)|STR SQL order by clause
  *
+ *  reverse_order_by => BOOL Reverse the default order by clause
+ *
  * 	limit => NULL (10)|INT SQL limit clause
  *
  * 	offset => NULL (0)|INT SQL offset clause
@@ -755,6 +757,7 @@ function elgg_get_entities(array $options = array()) {
 		'created_time_lower'	=>	ELGG_ENTITIES_ANY_VALUE,
 		'created_time_upper'	=>	ELGG_ENTITIES_ANY_VALUE,
 
+		'reverse_order_by'		=>	false,
 		'order_by' 				=>	'e.time_created desc',
 		'group_by'				=>	ELGG_ENTITIES_ANY_VALUE,
 		'limit'					=>	10,
@@ -860,6 +863,12 @@ function elgg_get_entities(array $options = array()) {
 
 	// Add access controls
 	$query .= get_access_sql_suffix('e');
+
+	// reverse order by
+	if ($options['reverse_order_by']) {
+		$options['order_by'] = elgg_sql_reverse_order_by_clause($options['order_by']);
+	}
+
 	if (!$options['count']) {
 		if ($options['group_by'] = sanitise_string($options['group_by'])) {
 			$query .= " GROUP BY {$options['group_by']}";