Paypal Merchant php sdk: trial launch errors

I downloaded the php paypal sdk trading version, version 3.6.106, and I had problems installing it and running the samples. On the github page, they say that no composer is needed, and we can use install.php. But where is install.php? I did not find it here https://github.com/paypal/merchant-sdk-php/tree/stable-php5.3

I tried using install.php from version 2.X, but I have the following error: mod_fcgid: stderr: PHP Fatal error: class 'PayPal \ CoreComponentTypes \ BasicAmountType' was not found in / var / www / merchant -sdk / samples / ExpressCheckout /DGsetExpressCheckout.php

Thanks in advance.