Ссылка на предыдущий и следующий товар в интернет-магазине

if ($Informationsystem_Controller_Show->item) {
   $oInformationsystem_Item = Core_Entity::factory('Informationsystem_Item', $Informationsystem_Controller_Show->item);

// Текущий элемент и группа
   $cur_elem = $Informationsystem_Controller_Show ->item;
   $cur_group = $oInformationsystem_Item   ->informationsystem_id;
   
   $oCore_QueryBuilder_Select = Core_QueryBuilder::select()
      ->select('informationsystem_items.path', 'informationsystem_items.name', 'informationsystem_items.sorting', 'informationsystem_items.id')
      ->from('informationsystem_items')
      ->where('informationsystem_items.sorting', '=', $cur_elem);
   
   $oCore_QueryBuilder_Select = Core_QueryBuilder::select()
      ->select('informationsystem_items.path', 'informationsystem_items.name', 'informationsystem_items.sorting', 'informationsystem_items.id')
      ->from('informationsystem_items')
      ->where('active', '=', 1)
      ->open()
      ->where('informationsystem_items.sorting', '<', $cur_elem)
      ->setAnd()
      ->where('informationsystem_items.informationsystem_id', '=', $cur_group)
      ->setAnd()
      ->where('informationsystem_items.deleted', '=', '0')
      ->close()
      ->clearOrderBy()
      ->orderBy('informationsystem_items.sorting', 'DESC')
      ->limit(1);
        $prev = $oCore_QueryBuilder_Select->execute()->asAssoc()->current(); $prev = $prev['path'];
   $prev_name = $oCore_QueryBuilder_Select->execute()->asAssoc()->current(); $prev_name = $prev_name['name'];

   $oCore_QueryBuilder_Select = Core_QueryBuilder::select()
      ->select('informationsystem_items.path', 'informationsystem_items.name', 'informationsystem_items.sorting', 'informationsystem_items.id')
      ->from('informationsystem_items')
      ->where('active', '=', 1)
      ->open()
      ->where('informationsystem_items.sorting', '>', $cur_elem)
      ->setAnd()
      ->where('informationsystem_items.informationsystem_id', '=', $cur_group)
      ->setAnd()
      ->where('informationsystem_items.deleted', '=', '0')
      ->close()
      ->clearOrderBy()
      ->orderBy('informationsystem_items.sorting')
      ->limit(1);
        $next = $oCore_QueryBuilder_Select->execute()->asAssoc()->current(); $next = $next ['path'];
   $next_name = $oCore_QueryBuilder_Select->execute()->asAssoc()->current(); $next_name = $next_name['name'];
   
   $Informationsystem_Controller_Show
      ->addEntity(Core::factory('Core_Xml_Entity')
                        ->name('neighboring_items')
                        ->addEntity(Core::factory('Core_Xml_Entity')->name('prev_item')     ->value($prev))
                        ->addEntity(Core::factory('Core_Xml_Entity')->name('prev_item_name')->value($prev_name))
                        ->addEntity(Core::factory('Core_Xml_Entity')->name('next_item')     ->value($next))
                        ->addEntity(Core::factory('Core_Xml_Entity')->name('next_item_name')->value($next_name)));
}

<xsl:template match="/informationsystem/informationsystem_item">
<xsl:variable name="link_path" select="/informationsystem/url" />
<xsl:variable name="prev_item" select="/informationsystem/neighboring_items/prev_item" />
<xsl:variable name="next_item" select="/informationsystem/neighboring_items/next_item" />
<xsl:variable name="prev_item_name" select="/informationsystem/neighboring_items/prev_item_name" />
<xsl:variable name="next_item_name" select="/informationsystem/neighboring_items/next_item_name" />

<!-- Б Л О К  -  окружающие элементы - Предыдущий-Следующий -->
<nav><ul class="pagination">
<xsl:choose>
<xsl:when test="$prev_item != ''"><li class="w-50 page-item text-right"><a class="page-link" href="{$link_path}{$prev_item}/">
<i class="fa fa-lg fa-arrow-circle-left mx-2" aria-hidden="true"></i><xsl:value-of select="$prev_item_name" /></a></li></xsl:when>
<xsl:otherwise><li class="w-50 page-item text-right disabled"><span class="page-link"><i class="fa fa-lg fa-arrow-circle-left mx-2" aria-hidden="true"></i>Начало</span></li></xsl:otherwise>
</xsl:choose>
<xsl:choose>
<xsl:when test="$next_item != ''"><li class="w-50 page-item"><a class="page-link" href="{$link_path}{$next_item}/">
<xsl:value-of select="$next_item_name" /><i class="fa fa-lg fa-arrow-circle-right mx-2" aria-hidden="true"></i></a></li></xsl:when>
<xsl:otherwise><li class="w-50 page-item disabled"><span class="page-link">Конец<i class="fa fa-lg fa-arrow-circle-right mx-2" aria-hidden="true"></i></span></li></xsl:otherwise>
</xsl:choose>
</ul></nav>

$cur_elem = $Informationsystem_Controller_Show ->item;