Encrytion

Hi Guys, I am not a security person - But just a thought I wanted to get my head round. When a PHP script is used to encrypt data to pass from server to browser - How can this be done b'cos if someone fills in something on a form and hits submit it can't be enrypted by the script until it gets to the server - at the same time if the server needs to send something to the browser then it cannot be sent encypted as the browser cannot decrypt it. I guess U could use SSL but then what is PHP encrytion mostly used for or am I missing something? This may be trivial to most but I just wondered ... Thanks Abe