How to get http request origin in php

Question

I want to create an API, and to authenticate API consumers, I will provide an API KEY, App-id and App-Secret. The problem is that I want to know where the http Request is coming from, so that I can know if the Host that is making que request is the registered Host. For example : www.someone.com has an app-id :0001, app-secret:1200 and api-key:458. If this credentials are used to make A request, I want to know if the requester is really www.someone.com

Answer 1

Generally, this header should do the job. Having the domain name in this header

header("Access-Control-Allow-Origin: " . $_SERVER['HTTP_ORIGIN'] . "");
// use domain name instead of $_SERVER['HTTP_ORIGIN'] above

but if you want to check for more info, use something like the following snippet

$allowed = array('domain1', 'domain2', 'domain3'); 

if(isset($_SERVER['HTTP_ORIGIN']) && in_array($_SERVER['HTTP_ORIGIN'], $allowed)){
    // SELECT credentials for this user account from database
    if(isset($_GET['api_key'], $_GET['app_secret'])
        && $_GET['api_key'] == 'api_key_from_db' 
        && $_GET['app_secret'] == 'app_secret_from_db'
    ){
        // all fine
    }else{
        // not allowed
    }
}else{
    // not allowed
}

If the users have to pass more data to your service, use POST instead of GET