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)
var_dump(strpos("My symbol utf-8 is the €.", "\xE2\x82\xAC")); // int(23)
There is a difference of using mb_strpos? Does't makes this work the same jobs? After all, does't strpos seek a string (multiple byte)? Is there a reason to use instead strpos?
For UTF-8, matching the byte sequence is exactly the same as matching character sequence.
So they both will find the needle at exactly the same point, but mb_strpos
counts full UTF-8 byte sequencees before the needle, where as strpos
calculates any bytes. So if your string had another multi-byte UTF-8 sequence, the results would be different:
strpos("My symbolö utf-8 is the €.", "€") !== mb_strpos("My symbolö utf-8 is the €.", "€", 0, "UTF-8")
But:
strpos("My symbol utf-8 is the €.", "€") === mb_strpos("My symbol utf-8 is the €.", "€", 0, "UTF-8")
Depending on the character set in use and the string being searched for, this may or may not make a difference.
strpos()
looks for the byte sequence that is passed as the needle.
mb_strpos()
does the same thing but it also respects character boundaries.
So strpos()
will match if the byte sequence occurs anywhere in the string. mb_strpos()
will only match if the byte sequence also represents a valid set of complete characters.
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
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