PHP mb_substr() not working correctly?

Question

This code

print mb_substr('éxxx', 0, 1);

prints an empty space :(

It is supposed to print the first character, é. This seems to work however:

print mb_substr('éxxx', 0, 2);

But it's not right, because (0, 2) means 2 characters...

score 49 · Accepted Answer · answered Dec 19 '12 at 13:17

49

Try passing the encoding parameter to mb_substr, as such:

print mb_substr('éxxx', 0, 1, 'utf-8');

The encoding is never detected automatically.

answered Dec 19 '12 at 13:17

povilasp

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The encoding is *never* detected automatically, it just always *defaults* to something. – deceze Dec 19 '12 at 13:20
Could it be a better idea if you use [`mb_detect_encoding`](http://php.net/manual/en/function.mb-detect-encoding.php) to *actually* try to detect the encoding? – Alvin Wong Dec 19 '12 at 13:20
4

@AlvinWong No. *Know* what encoding you're working with, there's no other way. – deceze Dec 19 '12 at 13:21
@Alvin Wong, that would be more correct, yes, but I could also say that using anything but utf-8 can be considered adventurous and marginal :) – povilasp Dec 19 '12 at 13:21
@deceze, wasn't sure, but thanks for the clarification, I updated the answer. – povilasp Dec 19 '12 at 13:21
tx that works. Can mb_substr work like `substr($string, 1)` without giving it the mb_strlen() argument ? – Alex Dec 19 '12 at 13:24
@Alex, that I think is another question, but my guess would be that yes - because the parameter is optional as it is in substr. – povilasp Dec 19 '12 at 13:27
yes, but that UTF-8 thing has to go after that argument. Anyway nvm, I`ll just use mb_strlen .. – Alex Dec 19 '12 at 13:28
3

OK, then how about [`mb_internal_encoding`](http://hk1.php.net/manual/en/function.mb-internal-encoding.php) instead of passing `"utf-8"` to all `mb_*` functions? Just like Álvaro G. Vicario has pointed out – Alvin Wong Dec 19 '12 at 13:31
@AlvinWong is right, it's better to look to mb_internal_encoding if this is not only function usage and you are planning to use a lot of mb_* functions through out your code. – povilasp Dec 19 '12 at 13:38

score 13 · Answer 2 · answered Dec 19 '12 at 13:23

In practice I've found that, in some systems, multi-byte functions default to ISO-8859-1 for internal encoding. That effectively ruins their ability to handle multi-byte text.

Setting a good default will probably fix this and some other issues:

mb_internal_encoding('UTF-8');

PHP mb_substr() not working correctly?

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