locale filter function running multiple times

Question

I'm running the following code:

 add_filter('locale', 'set_my_locale');
 function set_my_locale( $lang ) {
   $lang = "de";
   echo 'test';
   return $lang;
 }  

This is returning the correct 'de' language, but it is echoing out the 'test' 5 times.

Why is it echoing the 'test' 5 times?

The reason that I have the echo 'test'; in there is because I want to do some other checks in this function but it seems to run 5 times for some reason.

Answer 1

This is the expected behaviour. The locale filter is filtering the result of the get_locale() function. All this means is that get_locale() is being called at least 5 times.