This is a working CURL tested with PHP 7.4:
SSL verification is off, because it is curling an intranet server with no valid SSL certificate
$post = [
'band' => 'Abba',
'country' => 'Sweden'
];
$curl = curl_init();
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_TIMEOUT, 30);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
curl_setopt($curl, CURLOPT_POSTFIELDS, http_build_query($post));