String Encode, Array Decode

[By ZeNGiN]

I'm new to PHP, I started about 3 weeks ago.I have a string, which is used with $_POST to pass it to another page, the second page uses $_GET to get these url and split it as desired.My problem is that, in my first page I use a String, and I want to encrypt it, so that I can pass it as a plan text. In the second page I must decrypt it and get it as an array.So is there any encryption method or function I can use which is compatible with $_POST ( so I can send it to another page ) and decrypt it as an array ?I need this method, because the second page is actually connecting to website and is a payment method. So i don't want users to manually edit the url and lower the amount of $ for the product they get.tnx for your help.