<?php
$client_id = '3658695067033012';
$redirect_uri = 'https://sistema.compranet.com.co/marketplace/mercadolibre/callback.php';

$auth_url = "https://auth.mercadolibre.com.co/authorization?response_type=code&client_id=$client_id&redirect_uri=$redirect_uri";

header("Location: $auth_url");
exit;