mb_substr

(PHP 4 >= 4.0.6, PHP 5)

mb_substrGet part of string

Description

string mb_substr ( string $str , int $start [, int $length = NULL [, string $encoding = mb_internal_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.

Parameters

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. If omitted or NULL is passed, extract all characters to the end of the string.

encoding

The encoding parameter is the character encoding. If it is omitted, the internal character encoding value will be used.

Return Values

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

See Also

Коментарии

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) ); // returns "false"
var_dumpmb_substr'abc'5) ); // returns ""

?>

It's especially confusing when using mbstring with function overloading turned on.
2005-02-23 08:44:00
http://php5.kiev.ua/manual/ru/function.mb-substr.html
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
2005-08-02 11:33:36
http://php5.kiev.ua/manual/ru/function.mb-substr.html
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('Žąsinų'));
}

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>
2008-10-21 09:29:40
http://php5.kiev.ua/manual/ru/function.mb-substr.html
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($str01$enc), $enc).mb_substr($str1mb_strlen($str$enc), $enc);
}
?>

cheers!
2011-12-02 11:17:20
http://php5.kiev.ua/manual/ru/function.mb-substr.html
quick and dirty loop through multibyte string
<?php
function get_character_classes($string$encoding "UTF-8") {
   
$current_encoding mb_internal_encoding();
   
mb_internal_encoding($encoding);
   
$has = array();
   
$stringlength mb_strlen($string$encoding);
    for (
$i=0$i $stringlength$i++) {
       
$c mb_substr($string$i1);
        if ((
$c >= "0") && ($c <= "9")) {
           
$has['numeric'] = "numeric";
        } else if ((
$c >= "a") && ($c <= "z")) {
           
$has['alpha'] = "alpha";
           
$has['alphalower'] = 'alphalower';
        } else if ((
$c >= "A") && ($c <= "Z")) {
           
$has['alpha'] = "alpha";
           
$has['alphaupper'] = "alphaupper";
        } else if ((
$c == "$") || ($c == "£")) {
           
$has['currency'] = "currency";
        } else if ((
$c == ".") && ($has['decimal'])) {
           
$has['decimals'] = "decimals";
        } else if (
$c == ".") {
           
$has['decimal'] = "decimal";
        } else if (
$c == ",") {
           
$has['comma'] = "comma";
        } else if (
$c == "-") {
           
$has['dash'] = "dash";
        } else if (
$c == " ") {
           
$has['space'] = "space";
        } else if (
$c == "/") {
           
$has['slash'] = "slash";
        } else if (
$c == ":") {
           
$has['colon'] = "colon";
        } else if ((
$c >= " ") && ($c <= "~")) {
           
$has['ascii'] = "ascii";
        } else {
           
$has['binary'] = "binary";
        }
    }
   
mb_internal_encoding($current_encoding);
   
    return 
$has;
}

$string "1234asdfA£^_{}|}~žščř";
echo 
print_r(get_character_classes($string), true);
?>

Array
(
    [numeric] => numeric
    [alpha] => alpha
    [alphalower] => alphalower
    [alphaupper] => alphaupper
    [currency] => currency
    [ascii] => ascii
    [binary] => binary
)
2013-04-29 18:51:04
http://php5.kiev.ua/manual/ru/function.mb-substr.html
A serious pitfall when using mb_substr() set to HTML-ENTITIES encoding is that the function performs a number of conversions before returning the value, the worst one being that html special characters are not just counted but decoded.

<?php

mb_internal_encoding
("ISO-8859-1"); echo mb_internal_encoding(),"\n<br><br>\n";

$a='j&uuml;st &#228; &quot; simple &quot; &#26085;&#26412; &lt;b&gt;test&lt;/b&gt;';

echo 
mb_substr($a,0),"\n<br><br>\n";
// page source: j&uuml;st &#228; &quot; simple &quot; &#26085;&#26412; &lt;b&gt;test&lt;/b&gt;

echo mb_substr($a,0,strlen($a),'HTML-ENTITIES');
// page source: j&uuml;st &auml; " simple " &#26085;&#26412; <b>test</b>

?>
2013-09-27 21:18:22
http://php5.kiev.ua/manual/ru/function.mb-substr.html
As you often need to iterate over UTF-8 characters inside a string, you might be tempted to use mb_substr($text,$i,1).
The problem with this is that there is no "magic" way to find $i-th character inside UTF-8 string, other than reading it byte by byte from the begining. Thus a loop which calls mb_substr($text,$i,1) N times for all possible N values of $i, will take much longer than expected. The larger the $i gets, the longer is the search for $i-th letter. As characters are between 1 to 6 bytes long, one can convince oneself, that the execution time of such loop is actually Theta(N^2), which can be really slow even for moderately long texts.
One way to work around it is to first split your text into an array of letters using some smart preprocessing, and only then iterate over the array.
Here is the idea:
<?php
class Strings
{
  public static function 
len($a){
    return 
mb_strlen($a,'UTF-8');
  }
  public static function 
charAt($a,$i){
    return 
self::substr($a,$i,1);
  }
  public static function 
substr($a,$x,$y=null){
    if(
$y===NULL){
     
$y=self::len($a);
    }
    return 
mb_substr($a,$x,$y,'UTF-8');
  }
  public static function 
letters($a){
   
$len self::len($a);
    if(
$len==0){
      return array();
    }else if(
$len == 1){
      return array(
$a);
    }else{
      return 
Arrays::concat(
       
self::letters(self::substr($a,0,$len>>1)),
       
self::letters(self::substr($a,$len>>1))
      );
    }
  }
?>
As you can see, the Strings::letters($text) split the text recursively into two parts. Each level of the recursion requires time linear in the length of the string, and there is logarithmic number of levels, so the total runtime is O(N log N), which is still more than theoretically optimal O(N), but sadly this is the best idea I've got.
2015-08-05 18:10:32
http://php5.kiev.ua/manual/ru/function.mb-substr.html
you can make mb_substr working faster with long strings with usage of ucs-2 encoding.

<?php

header
('Content-Type: text/html; charset=utf-8');
echo 
'<meta http-equiv="Content-Type" content="text/html; charset=utf-8" >';

function 
test($string$encoding='utf8'){
   
$t1=microtime(true);
   
$textlen=mb_strlen($string);
   
$substr_len=3;
    for(
$i=0;$i<$textlen-$substr_len+1;$i++){
       
$substr=mb_substr($string,$i,$substr_len);
    }
    echo 
'mb_substr, '.$encoding.': '.(microtime(true)-$t1);
    echo 
' . check: ';
    if(
$encoding=='ucs2'){
       
$substr=mb_convert_encoding($substr,'utf-8','ucs2');
    }
   
var_dump$substr );
    echo 
' . <br>';
    echo 
'<br>';
}

$corpus_short=str_repeat('тест Тест ',1000);
// it works likewise slowly with "test Test" with utf8
mb_internal_encoding('utf-8');
test($corpus_short);

$corpus_short_ucs2=mb_convert_encoding($corpus_short,'ucs2','utf-8');
mb_internal_encoding('ucs2');
test($corpus_short_ucs2,'ucs2');

?>

output:

mb_substr, utf8: 0.26480984687805 . check: string(5) "ст " .

mb_substr, ucs2: 0.0048871040344238 . check: string(5) "ст " .
2016-06-27 19:06:10
http://php5.kiev.ua/manual/ru/function.mb-substr.html
Here is an example demonstrating the difference between `substr` and `mb_substr` functions:

1- When working with non UTF-8 characters, both functions behave the same and give the same output:

$str = 'abcdef';
echo substr($s, 0, 3); // abc
echo mb_substr($s, 0, 3); // abc

2- When working with UTF-8 characters, each function will behave differently and give a different result:

2.A- The 'substr' function works on the byte-level and with single-byte encoded characters only (doesn't support multibyte encoding). 

For example:

$str_utf8 = utf8_encode("déjà_vu");

If we do this:

echo substr($str_utf8, 0, 3); // dé
echo substr($str_utf8, 0, 2); // d�

=> That's because the special character "é" (and "à") is internally coded with two bytes:

PHP will start reading the first byte at index 0, which represents `d`, then move to the second byte, which is a part of the two-byte encoding of the character ` é `,  and since the length is set to 2, PHP will stop here and doesn't continue reading the third byte, so it doesn't recognize the character ` é ` and prints � instead of é.

2.B- The 'mb_substr' function works on the character-level and supports multibyte encoded characters. This means, PHP counts the number of characters only and doesn't take into consideration the number of bytes of their encoding, for example:

$str_utf8 = utf8_encode("déjà_vu");

echo mb_substr($str_utf8, 0, 4, "UTF-8"); // Déjà
echo mb_substr($str_utf8, 1, 4, "UTF-8"); // éjà_
echo mb_substr($str_utf8, 6, 4, "UTF-8"); // u
echo mb_substr($str_utf8, 7, 4, "UTF-8"); // ''
echo mb_substr($str_utf8, -2, "UTF-8"); // vu
echo mb_substr($str_utf8, -2, 1, "UTF-8"); // v
echo mb_substr($str_utf8, -2, 3, "UTF-8"); // vu
2023-12-30 13:28:31
http://php5.kiev.ua/manual/ru/function.mb-substr.html
Just wanted to add that not only the `start` can be a negative number, the `length` can be negative, too. And it works as expected.

mb_substr( "1234567890", 3, -4, "UTF-8" ) => "456".

So it cuts off the last 4 characters.
2024-03-25 12:17:05
http://php5.kiev.ua/manual/ru/function.mb-substr.html

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