问题:

when you have a charset different of UTF-8 and you need to put it on JSON format to migrate it to a DB, there are two methods that can be used in PHP, calling utf8_encode() and iconv(). I would like to know which one have better performance, and when is convenient to use one or another.

回答1:

when you have a charset different of UTF-8

Nope - utf8_encode() is suitable only for converting a ISO-8859-1 string to UTF-8. Iconv provides a vast number of source and target encodings.

Re performance, I have no idea how utf8_encode() works internally and what libraries it uses, but my prediction is there won't be much of a difference - at least not on "normal" amounts of data in the bytes or kilobytes. If in doubt, do a benchmark.

I tend to use iconv() because it's clearer that there is a conversion from character set A to character set B.

Also, iconv() provides more detailed control on what to do when it encounters invalid data. Adding //IGNORE to the target character set will cause it to silently drop invalid characters. This may be helpful in certain situations.