I'm working on an online form system which will be rolled out across multiple websites. I'd like all of the form data to be sent over an encrypted connection, however buying and installing SSL certificates for each website could get pricey pretty quickly! What I'm hoping to do is buy one certificate for the receiving server to which all other sites will be posting the data to. I'm thinking the solution would look something like this, but I am not sure if this method would ensure that the POST is encrypted. Will this method accept the certificate and transfer the data like I hope? I know with the PHP cURL method there are some active steps to tell PHP to accept and validate the SSL certificate. Would this HTML form do the trick I'm looking for? This form code is a sample of what would go on all of the other websites (which would not be on "example.com" in this scenario).
<form method="POST" action="https://www.example.com/get-post.php">
<input type="text" name="message">
<input type="submit" value="Send Securely">
Thank you in advance,