It is little difficult to get the right path in PHP sometime. PHP gets the path based on top page. To get the right path two functions are very useful - getcwd() and realpath().
To get what PHP is understanding of your supplied path for require/include, use realpath(). It will give you the path PHP has expanded to use. If PHP translated path is not correct then it will return bool(false).
Use this code
var_dump(realpath('your path'));
to see the Boolean value. If path is correct then it will return the real path.
To know where are you right now, you can use getcwd().
echo getcwd();
It will return the current execution path of php script. You need to consider this path when writing the relative path for include/require. Write your path related to this provided path.