The problem is that php is interpreting "%ce" as the url encoded character for Î.
So an easy solution would be to parse your input and encode it.
I don't know any simple way to access the .net encoding from B4PPC but you can do it by hand. You just have to get the ASCII code for the punctuation mark, convert that to Hex and then add a % in front of that number.
Please have a look at the attached example. (I added the Bitwise library for converting Dec to Hex)