快速结账整合第3步 - http重定向

Question

here's my question.

I've made a request to the PayPal server to obtain a token but now i don't know how to use it to pass it to the url in which i have to be redirected, and i don't understood in the documentation how this process works.

<form method="post" action="https://api-3t.sandbox.paypal.com/nvp">
    <input type="hidden" name="USER" value="user"/>
    <input type="hidden" name="PWD" value="pass"/>
    <input type="hidden" name="SIGNATURE" value="signature"/>
    <input type="hidden" name="VERSION" value="72.0"/>
    <input type="hidden" name="PAYMENTACTION" value="Sale"/>    
    <input name="AMT" value="19.95"/>
    <input type="hidden" name="RETURNURL" value="http://www.example.it"/>
    <input type="hidden" name="CANCELURL" value="http://www.example.it"/><br/><br/>
    <button style="background:#FFF; border:0px;" type="submit" name="METHOD" value="SetExpressCheckout"><img src="https://www.paypal.com/en_GB/GB/i/btn/btn_xpressCheckout.gif" value="SexExpressCheckout"></button>
</form>

In this case i send the data to the PayPal Sandbox server, i'm redirected there and there is the string in output with the token and the "Success" state.

Now i don't understand:

How can i be redirected to the login payment page (with the token inside the querystring) without landing on the Sandbox server url page?

I've watched the PHP SDK example about it but i possibly wanted to use a simple solution like described in the documentation.

Any tips to follow?

Thanks a lot