$sXML = download_page($url);
$xml = simplexml_load_string($sXML);ob_get_clean(); ob_start(); после контента записываете содержимое буфера в переменную $strAjaxItems = ob_get_contents(); ob_end_clean();
Ситуация сейчас выглядет по другому.
[url] => https://wisell.ru/bitrix/catalog_export/megamarket.php
[content_type] =>
[http_code] => 0
[header_size] => 0
[request_size] => 0
[filetime] => -1
[ssl_verify_result] => 0
[redirect_count] => 0
[total_time] => 31.385636
[namelookup_time] => 0.000159
[connect_time] => 0
[pretransfer_time] => 0
[size_upload] => 0
[size_download] => 0
[speed_download] => 0
[speed_upload] => 0
[download_content_length] => -1
[upload_content_length] => -1
[starttransfer_time] => 0
[redirect_time] => 0
[redirect_url] =>
[primary_ip] =>
[certinfo] => Array
(
)
[primary_port] => 0
[local_ip] =>
[local_port] => 0
[http_version] => 0
[protocol] => 0
[ssl_verifyresult] => 0
[scheme] =>
[appconnect_time_us] => 0
[connect_time_us] => 0
[namelookup_time_us] => 159
[pretransfer_time_us] => 0
[redirect_time_us] => 0
[starttransfer_time_us] => 0
[total_time_us] => 31385636
[effective_method] => GET
Но если загрузить файл через wget то весть xml на месте