Fatal error: Uncaught Exception: auto_return invalid. back_url.success must be defined in /home/osvaldo/public_html/data/mp/lib/mercadopago.php:419 Stack trace: #0 /home/osvaldo/public_html/data/mp/lib/mercadopago.php(432): MPRestClient::exec('POST', '/checkout/prefe...', Array, 'application/jso...') #1 /home/osvaldo/public_html/data/mp/lib/mercadopago.php(177): MPRestClient::post('/checkout/prefe...', Array) #2 /home/osvaldo/public_html/cons/mp.php(93): MP->create_preference(Array) #3 {main} thrown in /home/osvaldo/public_html/data/mp/lib/mercadopago.php on line 419