<?php
require_once(__DIR__ . '/vendor/autoload.php');

$config = new Meli\Configuration();
$servers = $config->getHostSettings();
// Auth URLs Options by country

// 1:  "https://auth.mercadolibre.com.ar"
// 2:  "https://auth.mercadolivre.com.br"
// 3:  "https://auth.mercadolibre.com.co"
// 4:  "https://auth.mercadolibre.com.mx"
// 5:  "https://auth.mercadolibre.com.uy"
// 6:  "https://auth.mercadolibre.cl"
// 7:  "https://auth.mercadolibre.com.cr"
// 8:  "https://auth.mercadolibre.com.ec"
// 9:  "https://auth.mercadolibre.com.ve"
// 10: "https://auth.mercadolibre.com.pa"
// 11: "https://auth.mercadolibre.com.pe"
// 12: "https://auth.mercadolibre.com.do"
// 13: "https://auth.mercadolibre.com.bo"
// 14: "https://auth.mercadolibre.com.py"

// Use the correct auth URL
$config->setHost($servers[1]["url"]);

// Or Print all URLs
print_r($servers);

// Or Print or Put the following URL in your browser window to obtain authorization:
// 
// http://auth.mercadolibre.com.ar/authorization?response_type=code&client_id=$APP_ID&redirect_uri=$YOUR_URL
?>

This will give you the url to redirect the user. You need to specify a callback url which will be the one that the user will redirected after a successfull authrization process.

Once the user is redirected to your callback url, you'll receive in the query string, a parameter named code. You'll need this for the second part of the process

<?php
require_once(__DIR__ . '/vendor/autoload.php');


$apiInstance = new Meli\Api\OAuth20Api(
    // If you want use custom http client, pass your client which implements `GuzzleHttp\ClientInterface`.
    // This is optional, `GuzzleHttp\Client` will be used as default.
    new GuzzleHttp\Client()
);
$grant_type = 'authorization_code';
$client_id = 'client_id_example'; // Your client_id
$client_secret = 'client_secret_example'; // Your client_secret
$redirect_uri = 'redirect_uri_example'; // Your redirect_uri
$code = 'code_example'; // The parameter CODE
$refresh_token = 'refresh_token_example'; // Your refresh_token

try {
    $result = $apiInstance->getToken($grant_type, $client_id, $client_secret, $redirect_uri, $code, $refresh_token);
    print_r($result);
} catch (Exception $e) {
    echo 'Exception when calling OAuth20Api->getToken: ', $e->getMessage(), PHP_EOL;
}
?>

<?php
require_once(__DIR__ . '/vendor/autoload.php');


$apiInstance = new Meli\Api\RestClientApi(
    // If you want use custom http client, pass your client which implements `GuzzleHttp\ClientInterface`.
    // This is optional, `GuzzleHttp\Client` will be used as default.
    new GuzzleHttp\Client()
);
$resource = 'resource_example'; // string | for example: items
$access_token = 'access_token_example'; // string | 
$body = new \stdClass; // object | 

try {
    $apiInstance->resourcePost($resource, $access_token, $body);
} catch (Exception $e) {
    echo 'Exception when calling RestClientApi->resourcePost: ', $e->getMessage(), PHP_EOL;
}
?>