Permitir CORS en PHP
Cabeceras para permitir CORS (Cross Origin Resource Sharing). Es decir, permitir llamadas desde aplicaciones que no están en el mismo dominio.
header('Access-Control-Allow-Origin: *');
header("Access-Control-Allow-Headers: X-API-KEY, Origin, X-Requested-With, Content-Type, Accept, Access-Control-Request-Method");
header("Access-Control-Allow-Methods: GET, POST, OPTIONS, PUT, DELETE");
header("Allow: GET, POST, OPTIONS, PUT, DELETE");
$method = $_SERVER['REQUEST_METHOD'];
if($method == "OPTIONS") {
die();
}