PHP Laravel API - How to limit request to a number of trusted hosts?

Assuming you are limiting guests by IP address or something similar, you could build a middleware like this:

namespace App\Http\Middleware;

use Closure;

class LimitAccess {

    public function handle($request, Closure $next)
    {
        if(env('APP_ENV')=='production') {
            $ipArray = ['127.0.0.1',...]; //Add trusted IP addresses here
            if (in_array(\Request::ip(), $ipArray)) {
                return $next($request);
            } else {
                return response("You are not allowed here!", 503);
            }
        } else {
            return $next($request);
        }
    }
}

For Laravel, you would register this middleware in the Http\Kernel.php under the $middlewareGroups array, like this:

protected $middlewareGroups = [
    'api' => [
        \App\Http\Middleware\LimitAccess::class
    ]
];

For Lumen, you can register by identifying the middleware with a short-hand key in the bootstrap/app.php file:

$app->routeMiddleware([
    'limit' => App\Http\Middleware\LimitAccess::class,
]);

Then you would apply it to the routes you want like this:

$router->get('url/you/want/to/limit', ['middleware' => 'limit', function () {
    //
}]);

This should do exactly what you want. You can obviously change out the IP address array to anything that you want.

Based on @eResourcesInc answer because I wanted to limit request to certain trusted clients (like some sister servers consuming an API) here's what I came up with:

Created new entry in .env file with my desired trusted client hostnames

TRUSTED_CLIENTS=specific.example.com|*.whatever.net|8-8-8-8.static.example.org

Then created the TrustedAccess middleware in App\Http\Middleware\TrustedAccess.php

namespace App\Http\Middleware;

use Illuminate\Http\Response;
use Closure;

class TrustedAccess
{
    private $trustedClients;

    public function __construct()
    {
        $this->trustedClients = [];
        if (env('TRUSTED_CLIENTS')) {
            $list = explode('|', env('TRUSTED_CLIENTS'));
            if ($list !== false && !empty($list)) {
                $this->trustedClients = $list;
            }
        }
    }

    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        if(env('APP_ENV')=='production') {
            $clientHostname = gethostbyaddr($request->getClientIp());
            $isTrusted = false;
            foreach ($this->trustedClients as $trustedClientHostname) {
                if (self::isHostnameMatch($clientHostname, $trustedClientHostname)) {
                    $isTrusted = true;
                    break;
                }
            }
            if ($isTrusted) {
                return $next($request);
            } else {
                return response()->json(['error'=>'Unauthorised'], Response::HTTP_UNAUTHORIZED);
            }
        } else {
            return $next($request);
        }
    }

    private static function isHostnameMatch($hostname, $trustedHostname)
    {
        if ($trustedHostname == '*' || $hostname == $trustedHostname) {
            return true;
        }
        // check if wildcard subdomain
        $subdomainDelimiterPosition = strpos($hostname, '.');
        if(strlen($trustedHostname) < 2 || $subdomainDelimiterPosition === false) {
            return false;
        }
        if (substr($trustedHostname, 0, 2) == '*.') {
            if (substr($trustedHostname, 1) == substr($hostname, $subdomainDelimiterPosition)) {
                return true;
            }
        }
        return false;
    }
}

For Lumen, I registered the middleware with a short-hand key in the bootstrap/app.php file:

$app->routeMiddleware([
    'trusted' => App\Http\Middleware\TrustedAccess::class,
]);

Then I applied it to the routes like this:

$router->get('url/I/want/to/limit', ['middleware' => 'trusted', function () {
    //
}]);

This is it. Please comment if any suggestions!