>>> $t=microtime(1);for ($i=0;$i<1000000;++$i)iconv("utf-8", "utf-8", "lsfkjhzlkfjhslfkjahlfkjashflkasjhflaskdfjhsalkdjfhsadlkfjh");microtime(1)-$t;
=> 1.7362649440765
>>> $t=microtime(1);for ($i=0;$i<1000000;++$i)mb_detect_encoding("lsfkjhzlkfjhslfkjahlfkjashflkasjhflaskdfjhsalkdjfhsadlkfjh", "utf-8", 1);microtime(1)-$t;
=> 1.3777210712433