<?php

function setAdditionalImages($id, $arHrefs){
    $propCode = 'MORE_PHOTO';
    $arFiles = array();
    foreach($arHrefs as $key => $href){
        $arFile = CFile::MakeFileArray($_SERVER["DOCUMENT_ROOT"].$href);
        $arFiles[$key] = array(
            'VALUE' => $arFile
        );
    }
    CIBlockElement::SetPropertyValueCode($id, $propCode, $arFiles );
}