I tried to call a post request using PHP code, but I got 401 Unauthorized error.

I tried to call a post request using PHP code, but I got 401 Unauthorized
error.

I tried to send a post request using this PHP code but throw me 401
Unauthorized error:
$username = 'MyDomain\testuser';
$password = '123456';
$url = 'http://10.20.30.40:8080/TargetPage.aspx';
$data = array(
'username' => $username,
'password' => $password,
'postdata' => 'InputParameter1=Test1&InputParameter2=Test2'
);
$options = array(
'http' => array
(
'method' => 'POST',
'header' => "Content-type:
application/x-www-form-urlencoded\r\n",
'content' => http_build_query($data)
)
);
$context = stream_context_create($options);
$result = file_get_contents($url, false, $context);