jQuery function loop don't stop after checkbox unchecked

I have a checkbox, which starts a loop of a function called "next". So far that work's correctly. Unckecked box should stop the function loop. That doesn't work. I found in the stackoverflow-forum, that it is necessary to declare a variable of the Interval-ID outside the if-else-statement. No success. Any ideas? This is the code:

 $('input[type="checkbox"]').click(function(){
      var intervalID = 0; 
      if($(this).is(":checked")){
          var intervalID = setInterval(next, 400);         
         }
           else if($(this).is(":not(:checked)")){
           clearInterval(intervalID);
        }
      }
  );

Regards