CORS example (server side).

service_example.php

<?php
if(empty($_SERVER['HTTP_ORIGIN'])) {
    die;
}
defined('LOG_DIR') OR define('LOG_DIR', dirname(__FILE__) . '/log/');
// domain => apiKey dictionary
$allowedDomains = array(
    'qualify-test-site.local' => 's0m3d0ma1n1d',
);
$host = parse_url($_SERVER['HTTP_ORIGIN'], PHP_URL_HOST);
if(!empty($host)
        && isset($allowedDomains[$host])
        && isset($_POST['apiKey'])
        && $allowedDomains[$host] == $_POST['apiKey']) {
    $headers = array(
        'Access-Control-Allow-Origin: ' . $_SERVER['HTTP_ORIGIN'],
        'Access-Control-Allow-Methods: POST, GET, OPTIONS',
        'Access-Control-Max-Age: 1000',
        'Access-Control-Allow-Headers: Content-Type',
    );
    foreach($headers as $header) {
        header($header);
    }
}
$response = var_export($_POST, true);
header('Content-Length: ' . strlen($response));
header('Content-Type: text/plain; charset=UTF-8');
echo $response;
//  log:
$separator = "\n" . str_repeat('-', 80) . "\n\n";
file_put_contents(
        LOG_DIR . 'post.txt',
        $response . $separator,
        FILE_APPEND
);