After transferring the site to apache php from windows to linux, ubuntu stopped sending post, where to dig?

Question

PHP

After migrating a site
from Windows 8.1 (Apache/2.2.25 (Win32) PHP/5.3.28)
to linux ubuntu (Apache/2.2.22 (Ubuntu) PHP 5.3.10-1ubuntu3.13)
, the post request was no longer sent, passing through cURL login and password from the form and receiving XML in response, quite successfully on Windows ...

if (strlen($_REQUEST['aName']) > 0 and strlen($_POST['aPass']) > 0) {
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, 'http://192.168.0.162/BlaBlaBla/authorization');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_HTTPAUTH, CURLAUTH_BASIC);
curl_setopt($curl, CURLOPT_USERPWD, "" . $_REQUEST['aName'] . ":" . $_POST['aPass']);
$r_xml = curl_exec($curl);
$dom = new domDocument("1.0", "utf-8");
$dom->loadXML($r_xml);

echo var_dump($r_xml);  
// string(448)
// DOMDocument::loadXML() [domdocument.loadxml]: Space required after the Public Identifier in Entity
// 413 
// does not allow request data with POST requests, or the amount of data provided in the request exceeds the capacity limit

Naturally, I already googled something, but recommendations about:
php.ini - post_max_size and others did not help ...
Any ideas?
Thanks in advance.