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PHP : Function Reference : Multibyte String Functions : mb_detect_encoding

mb_detect_encoding

Detect character encoding (PHP 4 >= 4.0.6, PHP 5)
string mb_detect_encoding ( string str [, mixed encoding_list [, bool strict]] )

mb_detect_encoding() detects character encoding in string str. It returns detected character encoding.

encoding_list is list of character encoding. Encoding order may be specified by array or comma separated list string.

If encoding_list is omitted, detect_order is used.

strict specifies whether to use the strict encoding detection or not. Default is FALSE.

Example 1396. mb_detect_encoding() example

<?php
/* Detect character encoding with current detect_order */
echo mb_detect_encoding($str);

/* "auto" is expanded to "ASCII,JIS,UTF-8,EUC-JP,SJIS" */
echo mb_detect_encoding($str, "auto");

/* Specify encoding_list character encoding by comma separated list */
echo mb_detect_encoding($str, "JIS, eucjp-win, sjis-win");

/* Use array to specify encoding_list  */
$ary[] = "ASCII";
$ary[] = "JIS";
$ary[] = "EUC-JP";
echo
mb_detect_encoding($str, $ary);
?>


See also mb_detect_order().

Code Examples / Notes » mb_detect_encoding

maarten

Sometimes 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.png


php-note-2005

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
?>


jaaks

Last example for verifying UTF-8 has one little bug. If 10xxxxxx byte occurs alone i.e. not in multibyte char, then it is accepted although it is against UTF-8 rules. Make following replacement to repair it.
Replace
        } // goto next char
with
        } else {
          return false; // 10xxxxxx occuring alone
        } // goto next char


chrigu

If 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.


rl

I 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)){
 $str=str_replace("\xE2\x82\xAC","&euro;",$str);
 $str=iconv("UTF-8","ISO-8859-1//TRANSLIT",$str);
 $str=str_replace("&euro;","\x80",$str);
}
If html-output is needed the last line is not necessary (and even unwanted).


sunggsun

from PHPDIG
   function isUTF8($str) {
       if ($str === mb_convert_encoding(mb_convert_encoding($str, "UTF-32", "UTF-8"), "UTF-8", "UTF-32")) {
           return true;
       } else {
           return false;
       }
   }


mark

For: rl at itfigures dot nl
Just note that your Euro symbol being \x80 is NOT standard for ISO-8859-1 or ISO-8859-15 as \x80 is a reserved character.
It is however "common practice" for windows developpers to mix windows-1252 and ISO-8859-1. Just convert to windows-1252 instead of ISO-8859-1 and you'll get your € symbol at the right place.


telemach

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('accentuée' , 'UTF-8, ISO-8859-1')
returns ISO-8859-1, while
mb_detect_encoding('accentué' , 'UTF-8, ISO-8859-1')
returns UTF-8
bottom line : an ending 'é' (and probably other accentuated chars) mislead mb_detect_encoding


chris

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);
}
?>


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mb_check_encoding
mb_convert_case
mb_convert_encoding
mb_convert_kana
mb_convert_variables
mb_decode_mimeheader
mb_decode_numericentity
mb_detect_encoding
mb_detect_order
mb_encode_mimeheader
mb_encode_numericentity
mb_ereg_match
mb_ereg_replace
mb_ereg_search_getpos
mb_ereg_search_getregs
mb_ereg_search_init
mb_ereg_search_pos
mb_ereg_search_regs
mb_ereg_search_setpos
mb_ereg_search
mb_ereg
mb_eregi_replace
mb_eregi
mb_get_info
mb_http_input
mb_http_output
mb_internal_encoding
mb_language
mb_output_handler
mb_parse_str
mb_preferred_mime_name
mb_regex_encoding
mb_regex_set_options
mb_send_mail
mb_split
mb_strcut
mb_strimwidth
mb_stripos
mb_stristr
mb_strlen
mb_strpos
mb_strrchr
mb_strrichr
mb_strripos
mb_strrpos
mb_strstr
mb_strtolower
mb_strtoupper
mb_strwidth
mb_substitute_character
mb_substr_count
mb_substr
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