<?php

require $_SERVER['DOCUMENT_ROOT'] . '/bitrix/modules/main/include/prolog_before.php';

$sFilePath = __DIR__ . $_SERVER['REQUEST_URI'];
$aFileInfo = pathinfo($sFilePath);
$aFileExtension = $aFileInfo['extension'];
if ($aFileExtension === 'xml') {
    header('Content-Type: application/xml; charset=utf-8');
}
$sFileContent = file_get_contents($sFilePath);

$aDefaultSite = CSite::GetList($by = "sort", $order = "ASC", ['DEFAULT' => 'Y'])->Fetch();

echo str_replace($aDefaultSite['SERVER_NAME'], $_SERVER['SERVER_NAME'], $sFileContent);