When should I use mb_strpos(); over strpos();?

Huh, looking at all those string functions, sometimes I get confused. One is using all the time mb_ functions, the other - plain ones, so the question is simple...

When should I use mb_strpos(); and when should I go with the plain one (strpos();)?

And, yes, I'm aware about t开发者_JS百科hat mb_ functions stand for multi-byte, but does it really mean, that if I'm working with only utf-8 encoded strings, I should stick with mb_ functions?

Thanks in advance!

You should use the mb_ functions whenever you expect to work with text that's not pure ASCII. I.e. you can work with the regular string functions, even if you're using UTF-8, as long as all the strings you're using them on only contain ASCII characters.

strpos('foobar', 'foo')  // fine in any (ASCII-compatible) encoding, including UTF-8
strpos('ふーばー', 'ふー') // won't work as expected, use mb_strpos instead

Yes, if working with UTF-8 (which is a multi-byte encoding : one character can use more than one byte), you should use the mb_* functions.

The non-mb functions will work on bytes, and not characters -- which is fine when 1 character == 1 byte ; but that's not the case with (for example) UTF-8.

I'd say yes, here's the description from the php documentation:

mbstring provides multibyte specific string functions that help you deal with multibyte encodings in PHP. In addition to that, mbstring handles character encoding conversion between the possible encoding pairs. mbstring is designed to handle Unicode-based encodings such as UTF-8 and UCS-2 and many single-byte encodings for convenience....

If you're not sure that the mb extension is loaded, you should check before because mb-string is a non-default extension.