(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)
mb_detect_encoding — Detect character encoding
$string, array|string|null $encodings = null, bool $strict = false): string|false
Detects the most likely character encoding for string string
from an ordered list of candidates.
Automatic detection of the intended character encoding can never be entirely reliable; without some additional information, it is similar to decoding an encrypted string without the key. It is always preferable to use an indication of character encoding stored or transmitted with the data, such as a "Content-Type" HTTP header.
This function is most useful with multibyte encodings, where not all sequences of bytes form a valid string. If the input string contains such a sequence, that encoding will be rejected, and the next encoding checked.
stringThe string being inspected.
encodingsA list of character encodings to try, in order. The list may be specified as an array of strings, or a single string separated by commas.
If encodings is omitted or null,
the current detect_order (set with the
mbstring.detect_order configuration option, or mb_detect_order()
function) will be used.
strict
Controls the behaviour when string
is not valid in any of the listed encodings.
If strict is set to false, the closest matching
encoding will be returned; if strict is set to true,
false will be returned.
The default value for strict can be set
with the
mbstring.strict_detection configuration option.
The detected character encoding, or false if the string is not valid
in any of the listed encodings.
| Versione | Descrizione |
|---|---|
| 8.2.0 |
mb_detect_encoding() will no longer return
the following non text encodings:
"Base64", "QPrint",
"UUencode", "HTML entities",
"7 bit" and "8 bit".
|
Example #1 mb_detect_encoding() example
<?php
// Detect character encoding with current detect_order
echo mb_detect_encoding($str);
// "auto" is expanded according to mbstring.language
echo mb_detect_encoding($str, "auto");
// Specify "encodings" parameter by list separated by comma
echo mb_detect_encoding($str, "JIS, eucjp-win, sjis-win");
// Use array to specify "encodings" parameter
$encodings = [
"ASCII",
"JIS",
"EUC-JP"
];
echo mb_detect_encoding($str, $encodings);
?>
Example #2 Effect of strict parameter
<?php
// 'áéóú' encoded in ISO-8859-1
$str = "\xE1\xE9\xF3\xFA";
// The string is not valid ASCII or UTF-8, but UTF-8 is considered a closer match
var_dump(mb_detect_encoding($str, ['ASCII', 'UTF-8'], false));
var_dump(mb_detect_encoding($str, ['ASCII', 'UTF-8'], true));
// If a valid encoding is found, the strict parameter does not change the result
var_dump(mb_detect_encoding($str, ['ASCII', 'UTF-8', 'ISO-8859-1'], false));
var_dump(mb_detect_encoding($str, ['ASCII', 'UTF-8', 'ISO-8859-1'], true));
?>Il precedente esempio visualizzerà:
string(5) "UTF-8" bool(false) string(10) "ISO-8859-1" string(10) "ISO-8859-1"
In some cases, the same sequence of bytes may form a valid string in multiple character encodings, and it is impossible to know which interpretation was intended. For instance, among many others, the byte sequence "\xC4\xA2" could be:
Example #3 Effect of order when multiple encodings match
<?php
$str = "\xC4\xA2";
// The string is valid in all three encodings, so the first one listed will be returned
var_dump(mb_detect_encoding($str, ['UTF-8', 'ISO-8859-1', 'ISO-8859-5']));
var_dump(mb_detect_encoding($str, ['ISO-8859-1', 'ISO-8859-5', 'UTF-8']));
var_dump(mb_detect_encoding($str, ['ISO-8859-5', 'UTF-8', 'ISO-8859-1']));
?>Il precedente esempio visualizzerà:
string(5) "UTF-8" string(10) "ISO-8859-1" string(10) "ISO-8859-5"
If you try to use mb_detect_encoding to detect whether a string is valid UTF-8, use the strict mode, it is pretty worthless otherwise.
<?php
$str = 'áéóú'; // ISO-8859-1
mb_detect_encoding($str, 'UTF-8'); // 'UTF-8'
mb_detect_encoding($str, 'UTF-8', true); // false
?>The documentation is no longer correct for php8.1 and mb_detect_encoding no longer supports order of encodings. The example outputs given in the documentation are also no longer correct for php8.1. This is somewhat explained here https://github.com/php/php-src/issues/8279
I understand the previous ambiguity in these functions, but in my option 8.1 should have deprecated mb_detect_encoding and mb_detect_order and came up with different functions. It now tries to find the encoding that will use the least amount of space regardless of the order, and I am not sure who needs that.
Below is an example function that will do what mb_detect_encoding was doing prior to the 8.1 change.
<?php
function mb_detect_enconding_in_order(string $string, array $encodings): string|false
{
foreach($encodings as $enc) {
if (mb_check_encoding($string, $enc)) {
return $enc;
}
}
return false;
}
?>Major undocumented breaking change since 8.1.7
https://3v4l.org/BLjZ3
Make sure to replace mb_detect_encoding with a loop of calls to mb_check_encodingIf you need to distinguish between UTF-8 and ISO-8859-1 encoding, list UTF-8 first in your encoding_list:
mb_detect_encoding($string, 'UTF-8, ISO-8859-1');
if you list ISO-8859-1 first, mb_detect_encoding() will always return ISO-8859-1.Based upon that snippet below using preg_match() I needed something faster and less specific. That function works and is brilliant but it scans the entire strings and checks that it conforms to UTF-8. I wanted something purely to check if a string contains UTF-8 characters so that I could switch character encoding from iso-8859-1 to utf-8.
I modified the pattern to only look for non-ascii multibyte sequences in the UTF-8 range and also to stop once it finds at least one multibytes string. This is quite a lot faster.
<?php
function detectUTF8($string)
{
return preg_match('%(?:
[\xC2-\xDF][\x80-\xBF] # non-overlong 2-byte
|\xE0[\xA0-\xBF][\x80-\xBF] # excluding overlongs
|[\xE1-\xEC\xEE\xEF][\x80-\xBF]{2} # straight 3-byte
|\xED[\x80-\x9F][\x80-\xBF] # excluding surrogates
|\xF0[\x90-\xBF][\x80-\xBF]{2} # planes 1-3
|[\xF1-\xF3][\x80-\xBF]{3} # planes 4-15
|\xF4[\x80-\x8F][\x80-\xBF]{2} # plane 16
)+%xs', $string);
}
?>A simple way to detect UTF-8/16/32 of file by its BOM (not work with string or file without BOM)
<?php
// Unicode BOM is U+FEFF, but after encoded, it will look like this.
define ('UTF32_BIG_ENDIAN_BOM' , chr(0x00) . chr(0x00) . chr(0xFE) . chr(0xFF));
define ('UTF32_LITTLE_ENDIAN_BOM', chr(0xFF) . chr(0xFE) . chr(0x00) . chr(0x00));
define ('UTF16_BIG_ENDIAN_BOM' , chr(0xFE) . chr(0xFF));
define ('UTF16_LITTLE_ENDIAN_BOM', chr(0xFF) . chr(0xFE));
define ('UTF8_BOM' , chr(0xEF) . chr(0xBB) . chr(0xBF));
function detect_utf_encoding($filename) {
$text = file_get_contents($filename);
$first2 = substr($text, 0, 2);
$first3 = substr($text, 0, 3);
$first4 = substr($text, 0, 3);
if ($first3 == UTF8_BOM) return 'UTF-8';
elseif ($first4 == UTF32_BIG_ENDIAN_BOM) return 'UTF-32BE';
elseif ($first4 == UTF32_LITTLE_ENDIAN_BOM) return 'UTF-32LE';
elseif ($first2 == UTF16_BIG_ENDIAN_BOM) return 'UTF-16BE';
elseif ($first2 == UTF16_LITTLE_ENDIAN_BOM) return 'UTF-16LE';
}
?>Beware of bug to detect Russian encodings
http://bugs.php.net/bug.php?id=38138I used Chris's function "detectUTF8" to detect the need from conversion from utf8 to 8859-1, which works fine. I did have a problem with the following iconv-conversion.
The problem is that the iconv-conversion to 8859-1 (with //TRANSLIT) replaces the euro-sign with EUR, although it is common practice that \x80 is used as the euro-sign in the 8859-1 charset.
I could not use 8859-15 since that mangled some other characters, so I added 2 str_replace's:
if(detectUTF8($str)){
$str=str_replace("\xE2\x82\xAC","€",$str);
$str=iconv("UTF-8","ISO-8859-1//TRANSLIT",$str);
$str=str_replace("€","\x80",$str);
}
If html-output is needed the last line is not necessary (and even unwanted).Just a note: Instead of using the often recommended (rather complex) regular expression by W3C (http://www.w3.org/International/questions/qa-forms-utf-8.en.php), you can simply use the 'u' modifier to test a string for UTF-8 validity:
<?php
if (preg_match("//u", $string)) {
// $string is valid UTF-8
}Function to detect UTF-8, when mb_detect_encoding is not available it may be useful.
<?php
function is_utf8($str) {
$c=0; $b=0;
$bits=0;
$len=strlen($str);
for($i=0; $i<$len; $i++){
$c=ord($str[$i]);
if($c > 128){
if(($c >= 254)) return false;
elseif($c >= 252) $bits=6;
elseif($c >= 248) $bits=5;
elseif($c >= 240) $bits=4;
elseif($c >= 224) $bits=3;
elseif($c >= 192) $bits=2;
else return false;
if(($i+$bits) > $len) return false;
while($bits > 1){
$i++;
$b=ord($str[$i]);
if($b < 128 || $b > 191) return false;
$bits--;
}
}
}
return true;
}
?>Much simpler UTF-8-ness checker using a regular expression created by the W3C:
<?php
// Returns true if $string is valid UTF-8 and false otherwise.
function is_utf8($string) {
// From http://w3.org/International/questions/qa-forms-utf-8.html
return preg_match('%^(?:
[\x09\x0A\x0D\x20-\x7E] # ASCII
| [\xC2-\xDF][\x80-\xBF] # non-overlong 2-byte
| \xE0[\xA0-\xBF][\x80-\xBF] # excluding overlongs
| [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2} # straight 3-byte
| \xED[\x80-\x9F][\x80-\xBF] # excluding surrogates
| \xF0[\x90-\xBF][\x80-\xBF]{2} # planes 1-3
| [\xF1-\xF3][\x80-\xBF]{3} # planes 4-15
| \xF4[\x80-\x8F][\x80-\xBF]{2} # plane 16
)*$%xs', $string);
} // function is_utf8
?>For detect UTF-8, you can use:
if (preg_match('!!u', $str)) { echo 'utf-8'; }
- NorihioriSometimes mb_detect_string is not what you need. When using pdflib for example you want to VERIFY the correctness of utf-8. mb_detect_encoding reports some iso-8859-1 encoded text as utf-8.
To verify utf 8 use the following:
//
// utf8 encoding validation developed based on Wikipedia entry at:
// http://en.wikipedia.org/wiki/UTF-8
//
// Implemented as a recursive descent parser based on a simple state machine
// copyright 2005 Maarten Meijer
//
// This cries out for a C-implementation to be included in PHP core
//
function valid_1byte($char) {
if(!is_int($char)) return false;
return ($char & 0x80) == 0x00;
}
function valid_2byte($char) {
if(!is_int($char)) return false;
return ($char & 0xE0) == 0xC0;
}
function valid_3byte($char) {
if(!is_int($char)) return false;
return ($char & 0xF0) == 0xE0;
}
function valid_4byte($char) {
if(!is_int($char)) return false;
return ($char & 0xF8) == 0xF0;
}
function valid_nextbyte($char) {
if(!is_int($char)) return false;
return ($char & 0xC0) == 0x80;
}
function valid_utf8($string) {
$len = strlen($string);
$i = 0;
while( $i < $len ) {
$char = ord(substr($string, $i++, 1));
if(valid_1byte($char)) { // continue
continue;
} else if(valid_2byte($char)) { // check 1 byte
if(!valid_nextbyte(ord(substr($string, $i++, 1))))
return false;
} else if(valid_3byte($char)) { // check 2 bytes
if(!valid_nextbyte(ord(substr($string, $i++, 1))))
return false;
if(!valid_nextbyte(ord(substr($string, $i++, 1))))
return false;
} else if(valid_4byte($char)) { // check 3 bytes
if(!valid_nextbyte(ord(substr($string, $i++, 1))))
return false;
if(!valid_nextbyte(ord(substr($string, $i++, 1))))
return false;
if(!valid_nextbyte(ord(substr($string, $i++, 1))))
return false;
} // goto next char
}
return true; // done
}
for a drawing of the statemachine see: http://www.xs4all.nl/~mjmeijer/unicode.png and http://www.xs4all.nl/~mjmeijer/unicode2.pngIt was helpful for my exec(...) call. When it returned cp866 or cp1251:
try {
$line = iconv('CP866', 'CP1251', $line);
} catch(Exception $e) {
}
return iconv('CP1251', 'UTF-8', $line);if the function " mb_detect_encoding" does not exist ...
... try:
<?php
// ----------------------------------------------------
if ( !function_exists('mb_detect_encoding') ) {
// ----------------------------------------------------------------
function mb_detect_encoding ($string, $enc=null, $ret=null) {
static $enclist = array(
'UTF-8', 'ASCII',
'ISO-8859-1', 'ISO-8859-2', 'ISO-8859-3', 'ISO-8859-4', 'ISO-8859-5',
'ISO-8859-6', 'ISO-8859-7', 'ISO-8859-8', 'ISO-8859-9', 'ISO-8859-10',
'ISO-8859-13', 'ISO-8859-14', 'ISO-8859-15', 'ISO-8859-16',
'Windows-1251', 'Windows-1252', 'Windows-1254',
);
$result = false;
foreach ($enclist as $item) {
$sample = iconv($item, $item, $string);
if (md5($sample) == md5($string)) {
if ($ret === NULL) { $result = $item; } else { $result = true; }
break;
}
}
return $result;
}
// ----------------------------------------------------------------
}
// ----------------------------------------------------
?>
example / usage of: mb_detect_encoding()
<?php
// ------------------------------------------------------
function str_to_utf8 ($str) {
if (mb_detect_encoding($str, 'UTF-8', true) === false) {
$str = utf8_encode($str);
}
return $str;
}
// ------------------------------------------------------
?>
$txtstr = str_to_utf8($txtstr);a) if the FUNCTION mb_detect_encoding is not available:
### mb_detect_encoding ... iconv ###
<?php
// -------------------------------------------
if(!function_exists('mb_detect_encoding')) {
function mb_detect_encoding($string, $enc=null) {
static $list = array('utf-8', 'iso-8859-1', 'windows-1251');
foreach ($list as $item) {
$sample = iconv($item, $item, $string);
if (md5($sample) == md5($string)) {
if ($enc == $item) { return true; } else { return $item; }
}
}
return null;
}
}
// -------------------------------------------
?>
b) if the FUNCTION mb_convert_encoding is not available:
### mb_convert_encoding ... iconv ###
<?php
// -------------------------------------------
if(!function_exists('mb_convert_encoding')) {
function mb_convert_encoding($string, $target_encoding, $source_encoding) {
$string = iconv($source_encoding, $target_encoding, $string);
return $string;
}
}
// -------------------------------------------
?>beware : even if you need to distinguish between UTF-8 and ISO-8859-1, and you the following detection order (as chrigu suggests)
mb_detect_encoding('accentu?e' , 'UTF-8, ISO-8859-1')
returns ISO-8859-1, while
mb_detect_encoding('accentu?' , 'UTF-8, ISO-8859-1')
returns UTF-8
bottom line : an ending '?' (and probably other accentuated chars) mislead mb_detect_encodingIn my environment (PHP 7.1.12),
"mb_detect_encoding()" doesn't work
where "mb_detect_order()" is not set appropriately.
To enable "mb_detect_encoding()" to work in such a case,
simply put "mb_detect_order('...')"
before "mb_detect_encoding()" in your script file.
Both
"ini_set('mbstring.language', '...');"
and
"ini_set('mbstring.detect_order', '...');"
DON'T work in script files for this purpose
whereas setting them in PHP.INI file may work.About function mb_detect_encoding, the link http://php.net/manual/zh/function.mb-detect-encoding.php , like this:
mb_detect_encoding('áéóú', 'UTF-8', true); // false
but now the result is not false, can you give me reason, thanks!<?php
$file = file_get_contents("somefile.txt");
$encodings = implode(',', mb_list_encodings());
echo mb_detect_encoding($file, $encodings, true);
?>
seems to work