Why is the request not being sent?

Question

PHP

Good afternoon!
I work through the API of a certain service.
You need to send a request to add a user.
I do so.

<?
$postdata = http_build_query(
    array(
        'api_username' => 'name',
        'api_password' => 'password',
    'MODULE' => 'Customer',
    'COMMAND' => 'add',
    'FirstName' => $_POST['FirstName'],
    'LastName' => $_POST['LastName'],
    'email' => $_POST['email'],
    'Phone' => $_POST['Phone'],
    'campaignId' => '3834',
    'Country' => $_POST['Country'],
    'birthday' => '1980-07-21',
    'gender' => 'male',
    'password' => $_POST['password'],
    'currency' => 'USD',
    'subCampaign' => 'qw'
    )
);

$opts = array('http' =>
    array(
        'method'  => 'POST',
        'header'  => 'Content-type: application/x-www-form-urlencoded',
        'content' => $postdata
    )
);

$context  = stream_context_create($opts);

$result = file_get_contents('http://proxy.optionrally.com/api/?', false, $context);

echo $result;
?>

But for some reason, not all fields are sent by the request.
Here is an example of sending a request.

FirstName=Artem&LastName=Name&email=a1rt2349%401gmail.com1&Phone=%2B373345327720&Country=8&password=123123123

The question is, why is it not being sent as expected and why are all the fields missing?
Tried with curl but nothing worked.
If the same request is generated, for example, manually and sent via GET, then everything works and all fields are sent.

Answer 1

Specify Content-Length.