Multibyte String 函数
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mb_check_encoding

(PHP 4 >= 4.4.3, PHP 5 >= 5.1.3)

mb_check_encoding — Check if the string is valid for the specified encoding

说明

bool mb_check_encoding ([ string $var = NULL [, string $encoding = mb_internal_encoding() ]] )

Checks if the specified byte stream is valid for the specified encoding. It is useful to prevent so-called "Invalid Encoding Attack".

参数

var

The byte stream to check. If it is omitted, this function checks all the input from the beginning of the request.

encoding

The expected encoding.

返回值

成功时返回 TRUE， 或者在失败时返回 FALSE.

Multibyte String 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: Check if the string is valid for the specified encoding

用户评论:

javalc6 at gmail dot com (24-Dec-2009 12:52)

In order to check if a string is encoded correctly in utf-8, I suggest the following function, that implements the RFC3629 better than mb_check_encoding():

<?php
function check_utf8($str) {
    $len = strlen($str);
    for($i = 0; $i < $len; $i++){
        $c = ord($str[$i]);
        if ($c > 128) {
            if (($c > 247)) return false;
            elseif ($c > 239) $bytes = 4;
            elseif ($c > 223) $bytes = 3;
            elseif ($c > 191) $bytes = 2;
            else return false;
            if (($i + $bytes) > $len) return false;
            while ($bytes > 1) {
                $i++;
                $b = ord($str[$i]);
                if ($b < 128 || $b > 191) return false;
                $bytes--;
            }
        }
    }
    return true;
} // end of check_utf8
?>

jbricci at ya-right dot com (02-Mar-2009 02:52)

This function does not check for bad byte sequence(s), it only checks if the byte stream is valid. If you want to verify a encoded string is valid, (IE: does not contain any bad byte sequences do the following...

<?php

/* check a strings encoded value */

function checkEncoding ( $string, $string_encoding )
{
    $fs = $string_encoding == 'UTF-8' ? 'UTF-32' : $string_encoding;

    $ts = $string_encoding == 'UTF-32' ? 'UTF-8' : $string_encoding;

    return $string === mb_convert_encoding ( mb_convert_encoding ( $string, $fs, $ts ), $ts, $fs );
}

/* test 1 variables */

$string = "\x00\x81";

$encoding = "Shift_JIS";

/* test 1 mb_check_encoding (test for bad byte stream) */

if ( true === mb_check_encoding ( $string, $encoding ) )
{
    echo 'valid (' . $encoding . ') encoded byte stream!<br />';
}
else
{
    echo 'invalid (' . $encoding . ') encoded byte stream!<br />';
}

/* test 1 checkEncoding (test for bad byte sequence(s)) */

if ( true === checkEncoding ( $string, $encoding ) )
{
    echo 'valid (' . $encoding . ') encoded byte sequence!<br />';
}
else
{
    echo 'invalid (' . $encoding . ') encoded byte sequence!<br />';
}

/* test 2 */

/* test 2 variables */

$string = "\x00\xE3";

$encoding = "UTF-8";

/* test 2 mb_check_encoding (test for bad byte stream) */

if ( true === mb_check_encoding ( $string, $encoding ) )
{
    echo 'valid (' . $encoding . ') encoded byte stream!<br />';
}
else
{
    echo 'invalid (' . $encoding . ') encoded byte stream!<br />';
}

/* test 2 checkEncoding (test for bad byte sequence(s)) */

if ( true === checkEncoding ( $string, $encoding ) )
{
    echo 'valid (' . $encoding . ') encoded byte sequence!<br />';
}
else
{
    echo 'invalid (' . $encoding . ') encoded byte sequence!<br />';
}

?>