Gather Password string after login

Hello – we are trying to create an app that will use the username and password string when logged in to also do some API calls to “login” to an API at the same time. To do this we need the password string that was used to login.

So – somehow – we want it so after login user is sent to a page, and we have their plain text password string that they entered on the login form.

I am not sure what all is involved in this, I am hoping that we do not have to create a totally customized ‘login.php” file from scratch so we can somehow retain that value.

Can anyone help on this? Thanks so much…