PHP: mb_substr - Manual (original) (raw)

(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)

mb_substr — Get part of string

Description

Parameters

string

The string to extract the substring from.

start

If start is non-negative, the returned string will start at the start'th position instring, counting from zero. For instance, in the string 'abcdef', the character at position 0 is 'a', the character at position 2 is 'c', and so forth.

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

length

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

encoding

The encodingparameter is the character encoding. If it is omitted or [null](reserved.constants.php#constant.null), the internal character encoding value will be used.

Return Values

mb_substr() returns the portion ofstring specified by thestart andlength parameters.

Changelog

Version Description
8.4.0 On invalid strings (those with encoding errors), character indices are now interpreted in the same manner as most other mbstring functions. This means that character indices returned by mb_strpos() can be passed directly.
8.0.0 encoding is nullable now.

See Also

Found A Problem?

qbolec at gmail dot com

10 years ago

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 <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>i</mi><mo>−</mo><mi>t</mi><mi>h</mi><mi>c</mi><mi>h</mi><mi>a</mi><mi>r</mi><mi>a</mi><mi>c</mi><mi>t</mi><mi>e</mi><mi>r</mi><mi>i</mi><mi>n</mi><mi>s</mi><mi>i</mi><mi>d</mi><mi>e</mi><mi>U</mi><mi>T</mi><mi>F</mi><mo>−</mo><mn>8</mn><mi>s</mi><mi>t</mi><mi>r</mi><mi>i</mi><mi>n</mi><mi>g</mi><mo separator="true">,</mo><mi>o</mi><mi>t</mi><mi>h</mi><mi>e</mi><mi>r</mi><mi>t</mi><mi>h</mi><mi>a</mi><mi>n</mi><mi>r</mi><mi>e</mi><mi>a</mi><mi>d</mi><mi>i</mi><mi>n</mi><mi>g</mi><mi>i</mi><mi>t</mi><mi>b</mi><mi>y</mi><mi>t</mi><mi>e</mi><mi>b</mi><mi>y</mi><mi>b</mi><mi>y</mi><mi>t</mi><mi>e</mi><mi>f</mi><mi>r</mi><mi>o</mi><mi>m</mi><mi>t</mi><mi>h</mi><mi>e</mi><mi>b</mi><mi>e</mi><mi>g</mi><mi>i</mi><mi>n</mi><mi>i</mi><mi>n</mi><mi>g</mi><mi mathvariant="normal">.</mi><mi>T</mi><mi>h</mi><mi>u</mi><mi>s</mi><mi>a</mi><mi>l</mi><mi>o</mi><mi>o</mi><mi>p</mi><mi>w</mi><mi>h</mi><mi>i</mi><mi>c</mi><mi>h</mi><mi>c</mi><mi>a</mi><mi>l</mi><mi>l</mi><mi>s</mi><mi>m</mi><msub><mi>b</mi><mi>s</mi></msub><mi>u</mi><mi>b</mi><mi>s</mi><mi>t</mi><mi>r</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">i-th character inside UTF-8 string, other than reading it byte by byte from the begining. Thus a loop which calls mb_substr(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.7429em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">i</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">−</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:0.7778em;vertical-align:-0.0833em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal">h</span><span class="mord mathnormal">c</span><span class="mord mathnormal">ha</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal">a</span><span class="mord mathnormal">c</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">er</span><span class="mord mathnormal">in</span><span class="mord mathnormal">s</span><span class="mord mathnormal">i</span><span class="mord mathnormal">d</span><span class="mord mathnormal">e</span><span class="mord mathnormal" style="margin-right:0.10903em;">U</span><span class="mord mathnormal" style="margin-right:0.13889em;">TF</span><span class="mspace" style="margin-right:0.2222em;"></span><span class="mbin">−</span><span class="mspace" style="margin-right:0.2222em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord">8</span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal">in</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.1667em;"></span><span class="mord mathnormal">o</span><span class="mord mathnormal">t</span><span class="mord mathnormal">h</span><span class="mord mathnormal" style="margin-right:0.02778em;">er</span><span class="mord mathnormal">t</span><span class="mord mathnormal">han</span><span class="mord mathnormal">re</span><span class="mord mathnormal">a</span><span class="mord mathnormal">d</span><span class="mord mathnormal">in</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal">i</span><span class="mord mathnormal">t</span><span class="mord mathnormal">b</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mord mathnormal">t</span><span class="mord mathnormal">e</span><span class="mord mathnormal">b</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mord mathnormal">b</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mord mathnormal">t</span><span class="mord mathnormal">e</span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mord mathnormal">ro</span><span class="mord mathnormal">m</span><span class="mord mathnormal">t</span><span class="mord mathnormal">h</span><span class="mord mathnormal">e</span><span class="mord mathnormal">b</span><span class="mord mathnormal">e</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal">inin</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord">.</span><span class="mord mathnormal" style="margin-right:0.13889em;">T</span><span class="mord mathnormal">h</span><span class="mord mathnormal">u</span><span class="mord mathnormal">s</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">oo</span><span class="mord mathnormal" style="margin-right:0.02691em;">pw</span><span class="mord mathnormal">hi</span><span class="mord mathnormal">c</span><span class="mord mathnormal">h</span><span class="mord mathnormal">c</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.01968em;">ll</span><span class="mord mathnormal">s</span><span class="mord mathnormal">m</span><span class="mord"><span class="mord mathnormal">b</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">s</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">u</span><span class="mord mathnormal">b</span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mopen">(</span></span></span></span>text,$i,1) N times for all possible N values of <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>i</mi><mo separator="true">,</mo><mi>w</mi><mi>i</mi><mi>l</mi><mi>l</mi><mi>t</mi><mi>a</mi><mi>k</mi><mi>e</mi><mi>m</mi><mi>u</mi><mi>c</mi><mi>h</mi><mi>l</mi><mi>o</mi><mi>n</mi><mi>g</mi><mi>e</mi><mi>r</mi><mi>t</mi><mi>h</mi><mi>a</mi><mi>n</mi><mi>e</mi><mi>x</mi><mi>p</mi><mi>e</mi><mi>c</mi><mi>t</mi><mi>e</mi><mi>d</mi><mi mathvariant="normal">.</mi><mi>T</mi><mi>h</mi><mi>e</mi><mi>l</mi><mi>a</mi><mi>r</mi><mi>g</mi><mi>e</mi><mi>r</mi><mi>t</mi><mi>h</mi><mi>e</mi></mrow><annotation encoding="application/x-tex">i, will take much longer than expected. The larger the </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">i</span><span class="mpunct">,</span><span class="mspace" style="margin-right:0.1667em;"></span><span class="mord mathnormal" style="margin-right:0.02691em;">w</span><span class="mord mathnormal">i</span><span class="mord mathnormal">llt</span><span class="mord mathnormal" style="margin-right:0.03148em;">ak</span><span class="mord mathnormal">e</span><span class="mord mathnormal">m</span><span class="mord mathnormal">u</span><span class="mord mathnormal">c</span><span class="mord mathnormal">h</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">o</span><span class="mord mathnormal">n</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal" style="margin-right:0.02778em;">er</span><span class="mord mathnormal">t</span><span class="mord mathnormal">han</span><span class="mord mathnormal">e</span><span class="mord mathnormal">x</span><span class="mord mathnormal">p</span><span class="mord mathnormal">ec</span><span class="mord mathnormal">t</span><span class="mord mathnormal">e</span><span class="mord mathnormal">d</span><span class="mord">.</span><span class="mord mathnormal" style="margin-right:0.13889em;">T</span><span class="mord mathnormal">h</span><span class="mord mathnormal">e</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">a</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal" style="margin-right:0.02778em;">er</span><span class="mord mathnormal">t</span><span class="mord mathnormal">h</span><span class="mord mathnormal">e</span></span></span></span>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($y===NULL){
      <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mo>=</mo><mi>s</mi><mi>e</mi><mi>l</mi><mi>f</mi><mo>:</mo><mo>:</mo><mi>l</mi><mi>e</mi><mi>n</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">y=self::len(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.625em;vertical-align:-0.1944em;"></span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">se</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">::</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mopen">(</span></span></span></span>a);
    }
    return mb_substr($a,$x,$y,'UTF-8');
  }
  public static function letters($a){
    <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>l</mi><mi>e</mi><mi>n</mi><mo>=</mo><mi>s</mi><mi>e</mi><mi>l</mi><mi>f</mi><mo>:</mo><mo>:</mo><mi>l</mi><mi>e</mi><mi>n</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">len = self::len(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">se</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal" style="margin-right:0.10764em;">f</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">::</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mopen">(</span></span></span></span>a);
    if($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.

boulahdidraid18 at gmail dot com

2 years ago

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

drraf at tlen dot pl

21 years ago

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.

p dot assenov at aip-solutions dot com

14 years ago

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, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>e</mi><mi>n</mi><mi>c</mi><mo stretchy="false">)</mo><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">enc), </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mord mathnormal">c</span><span class="mclose">)</span><span class="mpunct">,</span></span></span></span>enc).mb_substr($str, 1, mb_strlen($str, <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>e</mi><mi>n</mi><mi>c</mi><mo stretchy="false">)</mo><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">enc), </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mord mathnormal">c</span><span class="mclose">)</span><span class="mpunct">,</span></span></span></span>enc);
}
?>

cheers!

xiaogil at yahoo dot fr

20 years ago

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"; <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>m</mi><mi>y</mi><mi>s</mi><mi>t</mi><mi>r</mi><mi>i</mi><mi>n</mi><mi>g</mi><mo>=</mo><mi>m</mi><msub><mi>b</mi><mi>s</mi></msub><mi>u</mi><mi>b</mi><mi>s</mi><mi>t</mi><mi>r</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">mystring = mb_substr(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.854em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">m</span><span class="mord mathnormal">ys</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal">in</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">m</span><span class="mord"><span class="mord mathnormal">b</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">s</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">u</span><span class="mord mathnormal">b</span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mopen">(</span></span></span></span>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

public at luedi dot jp

2 years ago

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.

desmatic at gmail dot com

13 years ago

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();
    <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>s</mi><mi>t</mi><mi>r</mi><mi>i</mi><mi>n</mi><mi>g</mi><mi>l</mi><mi>e</mi><mi>n</mi><mi>g</mi><mi>t</mi><mi>h</mi><mo>=</mo><mi>m</mi><msub><mi>b</mi><mi>s</mi></msub><mi>t</mi><mi>r</mi><mi>l</mi><mi>e</mi><mi>n</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">stringlength = mb_strlen(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8889em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal">in</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mord mathnormal" style="margin-right:0.03588em;">g</span><span class="mord mathnormal">t</span><span class="mord mathnormal">h</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">m</span><span class="mord"><span class="mord mathnormal">b</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">s</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mord mathnormal" style="margin-right:0.01968em;">l</span><span class="mord mathnormal">e</span><span class="mord mathnormal">n</span><span class="mopen">(</span></span></span></span>string, $encoding);
    for ($i=0; <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>i</mi><mo>&lt;</mo></mrow><annotation encoding="application/x-tex">i &lt; </annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6986em;vertical-align:-0.0391em;"></span><span class="mord mathnormal">i</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">&lt;</span></span></span></span>stringlength; $i++) {
        <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mo>=</mo><mi>m</mi><msub><mi>b</mi><mi>s</mi></msub><mi>u</mi><mi>b</mi><mi>s</mi><mi>t</mi><mi>r</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">c = mb_substr(</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.4306em;"></span><span class="mord mathnormal">c</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:1em;vertical-align:-0.25em;"></span><span class="mord mathnormal">m</span><span class="mord"><span class="mord mathnormal">b</span><span class="msupsub"><span class="vlist-t vlist-t2"><span class="vlist-r"><span class="vlist" style="height:0.1514em;"><span style="top:-2.55em;margin-left:0em;margin-right:0.05em;"><span class="pstrut" style="height:2.7em;"></span><span class="sizing reset-size6 size3 mtight"><span class="mord mathnormal mtight">s</span></span></span></span><span class="vlist-s">​</span></span><span class="vlist-r"><span class="vlist" style="height:0.15em;"><span></span></span></span></span></span></span><span class="mord mathnormal">u</span><span class="mord mathnormal">b</span><span class="mord mathnormal">s</span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.02778em;">r</span><span class="mopen">(</span></span></span></span>string, $i, 1);
        if (($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
)

sanjuro at 1up-games dot com

12 years ago

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>

?>