Performing a search, I found some examples filling out forms from third-party sites and capturing the response. Most of these examples use the PHP cURL library.
On the gigasystem site, there is a code which shows you how to do it, including using captcha.
I'd like to go a bit further, log in to the site. I made changes to the code, but to no avail. I imagine I'm not sending the information correctly, that is, I do not know the exact identification of the parameters to be sent via POST.
Is there any way to find out?