Description:
------------
I have built an MVC (lightweight MVC) now in this is static class ("cleanData") 
with method for (POST, GET, URL) and use addSlashes on them,

the problem is when i use the return data in the empty function
("Fatal error: Can't use function return value in write context")

Test script:
---------------
class cleanData{
  public static function GET($key){
    return addslashes($_GET[$key]);
  }
}

if(empty(cleanData::GET("test"))){
  echo "empty";
}else{
  echo cleanData::GET("test");
}

Expected result:
----------------
if loaded with ?test=1 i should see
1 on output,

if loaded with ?test=, or without test in url i should see 
empty

Actual result:
--------------
Fatal error: Can't use function return value in write context