mb_strpos vs strpos, what's the difference?

Question

Yes: I know. We should use mb_* function when we\'re working with multibyte char. But when we\'re using strpos? Let\'s take a look this code (saved in utf-8)

Answer 1

I don't the find above example fully transparent and some users may be confused.

mb_string() should be used for multi-byte encoding, and what is multi-byte encoding you have explained in other questions, e.g. here.

Recently we use mostly UTF encodings as UTF-8 in this example (also UTF-16) which is multi-byte character set, however usually we use only ASCII character sets (e.g. for English) and the result of strpos and mb_strpos is identical for them.

The difference is visible when we use multi-byte characters, i.e. Chinese characters.

echo mb_internal_encoding(); //UTF-8

echo strpos('我在买绿茶', '在'); //3

echo mb_strpos('我在买绿茶', '在'); //1

So obviously it's applicable to Chinese characters, but also to emoji which some are not aware of.

To give wider view how it works I show length of the following string with strlen() and mb_strlen() functions.

echo strlen('我在买绿茶'); //15

echo mb_strlen('我在买绿茶'); //5