ADDED $sortByPostion flag to getChildren()

Author: Denis Ristic

app/code/Magento/Catalog/Model/ResourceModel/Category/Flat.php

@@ -602,9 +602,10 @@ public function isInRootCategoryList($category)
      * @param \Magento\Catalog\Model\Category $category
      * @param bool $recursive
      * @param bool $isActive
+     * @param bool $sortByPosition
      * @return array
      */
-    public function getChildren($category, $recursive = true, $isActive = true)
+    public function getChildren($category, $recursive = true, $isActive = true, $sortByPosition = false)
     {
         $select = $this->getConnection()->select()->from(
             $this->getMainStoreTable($category->getStoreId()),
@@ -619,6 +620,9 @@ public function getChildren($category, $recursive = true, $isActive = true)
         if ($isActive) {
             $select->where('is_active = ?', '1');
         }
+        if ($sortByPosition) {
+            $select->order('position ASC');
+        }
         $_categories = $this->getConnection()->fetchAll($select);
         $categoriesIds = [];
         foreach ($_categories as $_category) {