Your C# string has 12 bytes, a plus, and 10 bytes. Your PHP string has 6 bytes, a space, and 5 bytes. Hence in PHP you're using a special character set, capable of representing all required chars as a single byte; whereas in C# you're using two bytes per char. Suggestion: find out what the character set ("codepage") is you need, then use new Encoding(codepage) and its GetBytes() method. :)
Luc Pattyn
I only read code that is properly indented, and rendered in a non-proportional font; hint: use PRE tags in forum messages