21

I am trying to get the length of this unicode characters string

$text = 'نام سلطان م';
$length = strlen($text);
echo $length;

output

20

How it determines the length of unicode characters string?

Munib
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4 Answers4

42

strlen() is not handling multibyte characters correctly, as it assumes 1 char equals 1 byte, which is simply invalid for unicode. This behavior is clearly documented:

strlen() returns the number of bytes rather than the number of characters in a string.

The solution is to use mb_strlen() function instead (mb stands for multi byte) (see mb_strlen() docs).

EDIT

If for any reason change in code is not possible/doable, one may want to ensure string functions are automatically overloaded by multi-byte counterparts:

To use function overloading, set mbstring.func_overload in php.ini to a positive value that represents a combination of bitmasks specifying the categories of functions to be overloaded. It should be set to 1 to overload the mail() function. 2 for string functions, 4 for regular expression functions. For example, if it is set to 7, mail, strings and regular expression functions will be overloaded.

This is supported by PHP and documented here (note this feature is deprecated in PHP 7.2 and newer).

Please note that you may also need to edit your php.ini to ensure mb_string module is enabled. Available settings are documented here.

Marcin Orlowski
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    I wonder, what is the specific point for separating unicode/non-unicode functions? Why not always use `(mb_)` functions? – Ilia Dec 25 '14 at 09:06
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    Shortly - it's because PHP design (as language) sucks in many places and this includes UTF8 support too. PHP was not supporting multibyte encodings internally for ages, and that's why multibyte extension was created. You can have `mb_` used automatically by PHP using function overloading -> see http://php.net/manual/en/mbstring.overload.php but that's depends on PHP config so it sometimes may be better to directly use `mb_` if you cannot ensure it will be used other way. – Marcin Orlowski Dec 25 '14 at 09:51
  • Thanks for explanations, my friend, and especially for pointing at `overload`, missed that completely.. Cheers! – Ilia Dec 26 '14 at 14:51
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    Well for some reason mb_strlen($text) didn't work on my system directly. You may like to specify the encoding type: $len=mb_strlen($text,'UTF-8'); To be on the safe side. – tormuto Oct 13 '16 at 10:08
  • You may also want to edit your `php.ini` and set it up there. See: http://php.net/manual/en/mbstring.configuration.php – Marcin Orlowski Oct 14 '16 at 20:50
  • This difference between `strlen` and `mb_strlen` cost us tremendous error in a financial system we were programming. We found out we were overcharging some customers who were sending sms messages with unicode characters when we used `strlen`. Be careful guys, don't fall into the same trap we did. – Moses Ndeda Jan 14 '18 at 13:47
  • Unfortunately it also doesn't work with `sprintf` and padding. `mb_vsprintf` and `mb_sprintf` don't exists (?). – KumZ Apr 13 '21 at 21:44
3

You are looking for mb_strlen.

Jon
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2

Function strlnen does not count the number of characters, but the number of bytes. For multibyte characters it will return higher numbers.
Use mb_strlen() instead to count the actual count of characters.

Tomáš Zato - Reinstate Monica
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0

Just as an addendum to the other answers that reference mb_strlen():

If the php.in setting mbstring.func_overload has bit 2 set to 1, then strlen will count characters based on the default charset; otherwise it will count the number of bytes in the string

Ariel
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Mark Baker
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