handling encoded form data

Hello, I have a domain on a virtual web server that is fortunate to have PHP. I am not really new to programming (I'm a computer science undergrad) but I am a newbie to PHP. I really like it. It seems simple yet very powerful. I've already built two test pages that display a form value I send to it and a page that e-mails a static message to me using mail(). I want to know whether there is a built in function to turn the special format for form data (where the space is a +) back into the original input. I am not sure if urldecode is the right function, and I do not know the difference between rawurldecode and urldecode. Also, urldecode doesn't say anything about decoding the +, it just mentions decoding the hex values. Can someone point me in the right direction? Thanks. Regards, Alan Tu