Multibyte String 函数
在线手册：中文 英文
PHP手册

mb_substr

(PHP 4 >= 4.0.6, PHP 5)

mb_substr — Get part of string

说明

string mb_substr ( string $str , int $start [, int $length [, string $encoding ]] )

Performs a multi-byte safe substr() operation based on number of characters. Position is counted from the beginning of str. First character's position is 0. Second character position is 1, and so on.

参数

str

The string to extract the substring from.

start

Position of first character to use from str.

length

Maximum number of characters to use from str.

encoding

encoding 参数为字符编码。如果省略，则使用内部字符编码。

返回值

mb_substr() returns the portion of str specified by the start and length parameters.

参见

Multibyte String 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: Get part of string

用户评论:

santiago-php at zarate dot net dot ve (13-Mar-2012 04:57)

@qeremy

Actually you could just add the encoding you desire, and it would work perfectly (i.e: Give the same results as your approach)

<?php

    $str = "Büyük";
    print mb_substr($str, 0, 3); //Bü
    print mb_substr($str, 0, 3, 'UTF-8'); //Büy
    print substr_unicode($str, 3); //Büy
       
?>

qeremy [atta] gmail [dotta] com (27-Feb-2012 11:58)

A proper (logical) alternative for unicode strings;

<?php
function substr_unicode($str, $s, $l = null) {
    return join("", array_slice(
        preg_split("//u", $str, -1, PREG_SPLIT_NO_EMPTY), $s, $l));
}

$str = "Büyük";
$s = 0; // start from "0" (nth) char
$l = 3; // get "3" chars
echo substr($str, $s, $l) ."\n";    // Bü
echo mb_substr($str, $s, $l) ."\n"; // Bü
echo substr_unicode($str, $s, $l);  // Büy
?>

p dot assenov at aip-solutions dot com (02-Dec-2011 05:17)

I'm trying to capitalize only the first character of the string and tried some of the examples above but they didn't work. It seems mb_substr() cannot calculate the length of the string in multi-byte encoding (UTF-8) and it should be set explicitly. Here is the corrected version:

<?php
function mb_ucfirst($str, $enc = 'utf-8') {
    return mb_strtoupper(mb_substr($str, 0, 1, $enc), $enc).mb_substr($str, 1, mb_strlen($str, $enc), $enc);
}
?>

cheers!

levani9191 at gmail dot com (18-Jul-2010 11:37)

A simple code that check if the latest symbol in the string is a question mark and adds one if it doesn't...

<?php $string = (mb_substr($string, -1, 1, 'UTF-8') != '?') ? $string.'?' : $string; ?>

Anonymous (26-Feb-2010 01:15)

If start  is negative, the returned string will start at the start'th character from the end of string

dziamid at gmail dot com (06-Feb-2009 04:27)

Here is my solution to highlighting search queries in multibyte text:

<?php
function mb_highlight($data, $query, $ins_before, $ins_after)
{
 $result = '';
 while (($poz = mb_strpos(mb_strtolower($data), mb_strtolower($query))) !== false)
 {
       $query_len = mb_strlen ($query);
       $result .= mb_substr ($data, 0, $poz).
               $ins_before.
               mb_substr ($data, $poz, $query_len).
               $ins_after;
       $data = mb_substr ($data, $poz+$query_len);
 }
 return $result;
}
?>

Enjoy!

[EDIT BY danbrown AT php DOT net: Reclassified to a more appropriate function manual page.]

projektas at gmail dot com (21-Oct-2008 02:29)

First letter in upper case <hr />

<?php
header ('Content-type: text/html; charset=utf-8');

if (isset($_POST['check']) && !empty($_POST['check'])) {
    echo htmlspecialchars(ucfirst_utf8($_POST['check']));
} else {
    echo htmlspecialchars(ucfirst_utf8('??sin?'));
}

function ucfirst_utf8($str) {
    if (mb_check_encoding($str,'UTF-8')) {
        $first = mb_substr(
            mb_strtoupper($str, "utf-8"),0,1,'utf-8'
        );
        return $first.mb_substr(
            mb_strtolower($str,"utf-8"),1,mb_strlen($str),'utf-8'
        );
    } else {
        return $str;
    }
}
?>

<form method="post" action="" >
    <input type="input" name="check" />
    <input type="submit" />
</form>

Silvan (01-Sep-2007 11:30)

Passing null as length will not make mb_substr use it's default, instead it will interpret it as 0.
<?php
mb_substr($str,$start,null,$encoding); //Returns '' (empty string) just like substr()
?>
Instead use:
<?php
mb_substr($str,$start,mb_strlen($str),$encoding);
?>

xiaogil at yahoo dot fr (02-Aug-2005 04:33)

Thanks Darien from /freenode #php for the following example (a little bit changed).

It just prints the 6th character of $string.
You can replace the digits by the same in japanese, chinese or whatever language to make a test, it works perfect.

<?php
mb_internal_encoding("UTF-8");
$string = "0123456789";
$mystring = mb_substr($string,5,1);
echo $mystring;
?>

(I couldn't replace 0123456789 by chinese numbers for example here, because it's automatically converted into latin digits on this website, look :
&#38646;&#19968;&#20108;&#19977;&#22235;
&#20116;&#20845;&#19971;&#20843;&#20061;)

gilv

drraf at tlen dot pl (23-Feb-2005 02:44)

Note: If borders are out of string - mb_string() returns empty _string_, when function substr() returns _boolean_ false in this case.
Keep this in mind when using "===" comparisions.

Example code:
<?php

var_dump( substr( 'abc', 5, 2 ) ); // returns "false"
var_dump( mb_substr( 'abc', 5, 2 ) ); // returns ""

?>

It's especially confusing when using mbstring with function overloading turned on.