I am posting this to help others that may encounter a similar problem.
I have been doing some PHP development recently using Predis, a PHP Redis library. While instantiating the Redis\Client object I get
Warning: Unexpected character in input: '\' (ASCII=92) state=1 in .....
Problem was explained in this issue
http://github.com/nrk/predis/issues/closed#issue/11
If you are still running on PHP 5.2 you should use the backported version of Predis and not the mainline library which targets only PHP >= 5.3 (the backslash is the namespace separator in PHP 5.3).
More discussion of this change can be found here.
http://giorgiosironi.blogspot.com/2009/09/introspection-of-php-namespaces.html