The comma `:' in the first line of code is supposed to be a double comma `::'

As you state, this calling convention is not supported.  The reason relates to how the Zend engine parses PHP syntax and will not change in the forseeable future.  However, there is cleaner way to accomplish what you're attempting without using eval().

Try:

  return call_user_func(array($varclassname,'function'));

I notice that the documentation for call_user_func fails to note the ability to call static class methods in this way(changing category to documentation problem) and have added an additional paragraph and explanation explaining this.