Php string length utf8

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Please note that all the discussion about mb_str_replace in the comments is pretty pointless. str_replace works just fine with multibyte strings:

$string = ‘漢字はユニコード’ ;
$needle = ‘は’ ;
$replace = ‘Foo’ ;

echo str_replace ( $needle , $replace , $string );
// outputs: 漢字Fooユニコード

?>

The usual problem is that the string is evaluated as binary string, meaning PHP is not aware of encodings at all. Problems arise if you are getting a value «from outside» somewhere (database, POST request) and the encoding of the needle and the haystack is not the same. That typically means the source code is not saved in the same encoding as you are receiving «from outside». Therefore the binary representations don’t match and nothing happens.

PHP can input and output Unicode, but a little different from what Microsoft means: when Microsoft says «Unicode», it unexplicitly means little-endian UTF-16 with BOM(FF FE = chr(255).chr(254)), whereas PHP’s «UTF-16» means big-endian with BOM. For this reason, PHP does not seem to be able to output Unicode CSV file for Microsoft Excel. Solving this problem is quite simple: just put BOM infront of UTF-16LE string.

$unicode_str_for_Excel = chr(255).chr(254).mb_convert_encoding( $utf8_str, ‘UTF-16LE’, ‘UTF-8’);

SOME multibyte encodings can safely be used in str_replace() and the like, others cannot. It’s not enough to ensure that all the strings involved use the same encoding: obviously they have to, but it’s not enough. It has to be the right sort of encoding.

UTF-8 is one of the safe ones, because it was designed to be unambiguous about where each encoded character begins and ends in the string of bytes that makes up the encoded text. Some encodings are not safe: the last bytes of one character in a text followed by the first bytes of the next character may together make a valid character. str_replace() knows nothing about «characters», «character encodings» or «encoded text». It only knows about the string of bytes. To str_replace(), two adjacent characters with two-byte encodings just looks like a sequence of four bytes and it’s not going to know it shouldn’t try to match the middle two bytes.

While real-world examples can be found of str_replace() mangling text, it can be illustrated by using the HTML-ENTITIES encoding. It’s not one of the safe ones. All of the strings being passed to str_replace() are valid HTML-ENTITIES-encoded text so the «all inputs use the same encoding» rule is satisfied.

$string = ‘x<y’ ;
mb_internal_encoding ( ‘HTML-ENTITIES’ );

echo «Text length: » , mb_strlen ( $string ), «\tString length: » , strlen ( $string ), » . » , $string , «\n» ;
// Three characters, six bytes; the text reads «x

$newstring = str_replace ( ‘l’ , ‘g’ , $string );
echo «Text length: » , mb_strlen ( $newstring ), «\tString length: » , strlen ( $newstring ), » . » , $newstring , «\n» ;
// Three characters, six bytes, but now the text reads «x>y»; the wrong characters have changed.

$newstring = str_replace ( ‘;’ , ‘:’ , $string );
echo «Text length: » , mb_strlen ( $newstring ), «\tString length: » , strlen ( $newstring ), » . » , $newstring , «\n» ;
// Now even the length of the text is wrong and the text is trashed.

?>

Even though neither ‘l’ nor ‘;’ appear in the text «xy» and in the other it broke the encoding completely.

One more reason to use UTF-8 if you can, I guess.

A small note for those who will follow rawsrc at gmail dot com’s advice: mb_split uses regular expressions, in which case it may make sense to use built-in function mb_ereg_replace.

Note that some of the multi-byte functions run in O(n) time, rather than constant time as is the case for their single-byte equivalents. This includes any functionality requiring access at a specific index, since random access is not possible in a string whose number of bytes will not necessarily match the number of characters. Affected functions include: mb_substr(), mb_strstr(), mb_strcut(), mb_strpos(), etc.

function mb_str_pad ( $input , $pad_length , $pad_string , $pad_style , $encoding = «UTF-8» ) <
return str_pad ( $input ,
strlen ( $input )- mb_strlen ( $input , $encoding )+ $pad_length , $pad_string , $pad_style );
>
?>

Yet another single-line mb_trim() function

function mb_trim ( $string , $trim_chars = ‘\s’ ) return preg_replace ( ‘/^[‘ . $trim_chars . ‘]*(?U)(.*)[‘ . $trim_chars . ‘]*$/u’ , ‘\\1’ , $string );
>
$string = ‘ «some text.» ‘ ;
echo mb_trim ( $string , ‘\s».’ );
//some text
?>

This would be one way to create a multibyte substr_replace function

function mb_substr_replace ( $output , $replace , $posOpen , $posClose ) <
return mb_substr ( $output , 0 , $posOpen ). $replace . mb_substr ( $output , $posClose + 1 );
>
?>

str_replace is NOT multi-bite safe.

This Ukrainian word gives a bug when used in the next code: відео

$result = str_replace(str_split($rubishcharacters), ‘ ‘, $searchstring);

PHP5 has no mb_trim(), so here’s one I made. It work just as trim(), but with the added bonus of PCRE character classes (including, of course, all the useful Unicode ones such as \pZ).

Unlike other approaches that I’ve seen to this problem, I wanted to emulate the full functionality of trim() — in particular, the ability to customise the character list.

/**
* Trim characters from either (or both) ends of a string in a way that is
* multibyte-friendly.
*
* Mostly, this behaves exactly like trim() would: for example supplying ‘abc’ as
* the charlist will trim all ‘a’, ‘b’ and ‘c’ chars from the string, with, of
* course, the added bonus that you can put unicode characters in the charlist.
*
* We are using a PCRE character-class to do the trimming in a unicode-aware
* way, so we must escape ^, \, — and ] which have special meanings here.
* As you would expect, a single \ in the charlist is interpretted as
* «trim backslashes» (and duly escaped into a double-\ ). Under most circumstances
* you can ignore this detail.
*
* As a bonus, however, we also allow PCRE special character-classes (such as ‘\s’)
* because they can be extremely useful when dealing with UCS. ‘\pZ’, for example,
* matches every ‘separator’ character defined in Unicode, including non-breaking
* and zero-width spaces.
*
* It doesn’t make sense to have two or more of the same character in a character
* class, therefore we interpret a double \ in the character list to mean a
* single \ in the regex, allowing you to safely mix normal characters with PCRE
* special classes.
*
* *Be careful* when using this bonus feature, as PHP also interprets backslashes
* as escape characters before they are even seen by the regex. Therefore, to
* specify ‘\\s’ in the regex (which will be converted to the special character
* class ‘\s’ for trimming), you will usually have to put *4* backslashes in the
* PHP code — as you can see from the default value of $charlist.
*
* @param string
* @param charlist list of characters to remove from the ends of this string.
* @param boolean trim the left?
* @param boolean trim the right?
* @return String
*/
function mb_trim ( $string , $charlist = ‘\\\\s’ , $ltrim = true , $rtrim = true )
<
$both_ends = $ltrim && $rtrim ;

if( $both_ends )
<
$pattern_middle = $left_pattern . ‘|’ . $right_pattern ;
>
elseif( $ltrim )
<
$pattern_middle = $left_pattern ;
>
else
<
$pattern_middle = $right_pattern ;
>

return preg_replace ( «/ $pattern_middle /usSD» , » , $string ) );
>
?>

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Php string length utf8

Для того, чтобы определить/найти длину строки в php вам понадобится:

И поместим в неё некий текст.

И выведем найденную длину строки в php с помощью echo.

Код нахождения длины строки php.

$text=’length str’; //длина строки : 10

Пример нахождения длины строки php.

Для того, чтобы увидеть действие кода примера «определения длины строки в php» — разместим выше приведенный код прямо здесь:

Неправильное определение длины строки в php!

Сверху я разобрал правильное определение длины строки!

Но может и приведенная функция определять длину строки неправильно!

Для иллюстрации этого давайте приведем пример, для этого вам понадобится:

Теория и код из выше приведенного пункта.

+ Изменим текст в переменной:

Все остальное такое же. и соберем весь код:

Код неправильного определения длины строки в php:

$text=’длина строки’; //длина строки : 12

echo $length_str_cyrillic ; //длина строки : 23

Пример работы Кода неправильного определения длины строки в php:

Почему Неправильное определение длины строки в php?

Выше вы увидели неправильное определение длины строки в php!

Давайте разберем, почему такое произошло!

Разбор ошибки неправильного определения длины строки в php:

Как видим. что-то здесь не правильно.

Если вы посчитаете длину строки в приведенном примере, то окажется, что длина строки равна 12.

Но результат неожиданно выводится, что длина строки php равна 23.

Не буду внедряться глубоко в тему, но :

На моём сайте кодировка utf-8 — это, так называемая «многобайтовая кодировка» — смотри отличие многобайтовой кодировки от однобайтовой кодировки.

Другими словами — в данном примере вы видите. неправильный подсчет длины строки из-за того, что каждый символ данной строки имеет две длины. вместо одной.

Всего букв 11, умножаем на 2 :

Вот получилась как неправильная длина строки!

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