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PHP - Manual: mb_encode_mimeheader

2024-11-14

mb_encode_mimeheader

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

mb_encode_mimeheader — 为 MIME 头编码字符串

说明

mb_encode_mimeheader(
    string $string,
    ?string $charset = null,
    ?string $transfer_encoding = null,
    string $newline = "\r\n",
    int $indent = 0
): string

按 MIME 头编码方案将指定的字符串 string 进行编码。

参数

string

要编码的 string。 它的编码应该和 mb_internal_encoding() 一样。

charset

charset 指定了 str 的字符集名。 其默认值由当前的 NLS 设置（mbstring.language）来确定。

transfer_encoding

transfer_encoding 指定了 MIME 的编码方案。 它可以是 "B"（Base64）也可以是 "Q"（Quoted-Printable）。 如果未设置，将回退为 "B"。

newline

newline 指定了 EOL（行尾）标记，使 mb_encode_mimeheader() 执行了一个换行（» RFC 文档中规定，超过长度的一行将换成多行，当前该长度硬式编码为 74 个字符）。 如果没有设定，则回退为 "\r\n" (CRLF)。

indent

首行缩进（header 里 string 前的字符数目）。

返回值

转换后的字符串版本以 ASCII 形式表达。

更新日志

版本 说明
8.0.0 charset 和 transfer_encoding 现在可以为空。

范例

示例 #1 mb_encode_mimeheader() 例子

<?php
$name = "太郎"; // kanji
$mbox = "kru";
$doma = "gtinn.mon";
$addr = '"' . addcslashes(mb_encode_mimeheader($name, "UTF-7", "Q"), '"') . '" <' . $mbox . "@" . $doma . ">";
echo $addr;
?>

以上例程会输出：

"=?UTF-7?Q?+WSqQzg-?=" <kru@gtinn.mon>

注释

注意:

这个函数没有设计成据更高级上下文的中断点来换行（单词边界等）。 这个特性将导致意外的空格可能会让原始字符串看上去很乱。

参见

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User Contributed Notes 10 notes

up
8
stormflyCUT at hyh dot pl
16 years ago
Some solution for using national chars and have problem with UTF-8 for example in mail subject. Before you use mb_encode_mimeheader with UTF-8 set mb_internal_encoding('UTF-8').
up
2
tokul at users dot sourceforge dot net
14 years ago
mb_encode_mimeheader() depends on correct mbstring.internal_encoding setting. It tries to convert $str from internal encoding to $charset. If you ignore mbstring internal encoding, function might encode strings incorrectly even when $str character set matches $charset
up
2
gullevek at gullevek dot org
18 years ago
Read this FIRST: http://bugs.php.net/bug.php?id=23192 because mb_encode_mimeheaders is BUGGY!

a work around for the multibyte broken error for too long subjects for ISO-2022-JP:

$pos=0;
$split=36; // after 36 single bytes characters, if then comes MB, it is broken
while ($pos<mb_strlen($string,$encoding))
{
  $output=mb_strimwidth($string,$pos,$split,"",$encoding);
  $pos+=mb_strlen($output,$encoding);
  $_string.=(($_string)?' ':'').mb_encode_mimeheader($output,$encoding);
}
$string=$_string;

is not the best, but it works
up
1
nigrez at nius dot waw dot pl
16 years ago
True, function is broken (PHP5.1, encoding from UTF-8 with pl_PL charset). Below is about 15% faster version of proposed _mb_mime_encode. Also it has header more like othe mb_* functions and doesn't trigger any errors/warnings/notices.

<?php

function mb_mime_header($string, $encoding=null, $linefeed="\r\n") {
  if(!$encoding) $encoding = mb_internal_encoding();
  $encoded = '';

  while($length = mb_strlen($string)) {
    $encoded .= "=?$encoding?B?"
             . base64_encode(mb_substr($string,0,24,$encoding))
             . "?=$linefeed";

    $string = mb_substr($string,24,$length,$encoding);
  }

  return $encoded;
}

?>
up
1
gullevek at gullevek dot org
16 years ago
My first post was around 2003, and still the mb_mime_header is broken. It is *NOT* usable with longer subjects, and mostly unusable with anything else than japanese.

iwakura at junx dot org is also not working for me, it produces also some gargabe.

I updated my old function (the one I posted 2003) and I tested it with overlong subjects in UTF-8, ISO-2022-JP (japanese), GB2312 (simplified chinese) and EUC-KR (korean) and I got readable results in thunderbird, mail.app, outlook, etc.

<?php

function _mb_mime_encode($string, $encoding)
{
    $pos = 0;
    // after 36 single bytes characters if then comes MB, it is broken
    // but I trimmed it down to 24, to stay 100% < 76 chars per line
    $split = 24;
    while ($pos < mb_strlen($string, $encoding))
    {
        $output = mb_strimwidth($string, $pos, $split, "", $encoding);
        $pos += mb_strlen($output, $encoding);
        $_string_encoded = "=?".$encoding."?B?".base64_encode($output)."?=";
        if ($_string)
            $_string .= "\r\n";
        $_string .= $_string_encoded;
    }
    $string = $_string;
    return $string;
}

?>
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1
Anonymous
13 years ago
I could not find a PHP function to MIME encode the name for a n email address.

Input   = "Karl Müller<kmueller@gmx.de>"
Output = "Karl%20M%FCller<kmueller@gmx.de>"

I wrote it on my own:

<?php
// required to encode names in email addresses   
// replace " " with "%20"
// replace "ü" with "%FC"
// replace "%" with "%25"      etc....
// Use "%" as Delimiter for MIME
// Use "=" as Delimiter for Quoted Printable
// Input string must be UTF8 encoded
public static function EncodeMime($Text, $Delimiter)
{
    $Text = utf8_decode($Text);
    $Len  = strlen($Text);
    $Out  = "";
    for ($i=0; $i<$Len; $i++)
    {
        $Chr = substr($Text, $i, 1);
        $Asc = ord($Chr);

        if ($Asc > 0x255) // Unicode not allowed
        {
            $Out .= "?";
        }
        else if ($Chr == " " || $Chr == $Delimiter || $Asc > 127)
        {
            $Out .= $Delimiter . strtoupper(bin2hex($Chr));
        }
        else $Out .= $Chr;
    }
    return $Out;
}
?>
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0
paravoid
16 years ago
If mb_ version doesn't work for you in MIME-B mode:

function encode_mimeheader($string, $charset=null, $linefeed="\r\n") {
    if (!$charset)
        $charset = mb_internal_encoding();

    $start = "=?$charset?B?";
    $end = "?=";
    $encoded = '';

    /* Each line must have length <= 75, including $start and $end */
    $length = 75 - strlen($start) - strlen($end);
    /* Average multi-byte ratio */
    $ratio = mb_strlen($string, $charset) / strlen($string);
    /* Base64 has a 4:3 ratio */
    $magic = $avglength = floor(3 * $length * $ratio / 4);

    for ($i=0; $i <= mb_strlen($string, $charset); $i+=$magic) {
        $magic = $avglength;
        $offset = 0;
        /* Recalculate magic for each line to be 100% sure */
        do {
            $magic -= $offset;
            $chunk = mb_substr($string, $i, $magic, $charset);
            $chunk = base64_encode($chunk);
            $offset++;
        } while (strlen($chunk) > $length);
        if ($chunk)
            $encoded .= ' '.$start.$chunk.$end.$linefeed;
    }
    /* Chomp the first space and the last linefeed */
    $encoded = substr($encoded, 1, -strlen($linefeed));

    return $encoded;
}
up
0
chappy at citromail dot hu
16 years ago
In countries where there's non-us ASCII, it's a very good example, for sending mail:

mb_internal_encoding('iso-8859-2');
setlocale(LC_CTYPE, 'hu_HU');

function encode($str,$charset){
    $str=mb_encode_mimeheader(trim($str),$charset, 'Q', "\n\t");
    return $str;
}

print encode('the text with spec. chars: &#337; &#368; &#336; &#369;, ?','iso-8859-2');

It creates a 7bit string
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-2
iwakura at junx dot org
16 years ago
i think mb_encode_mimeheader still have bug. here is sample code:

function mb_encode_mimeheader2($string, $encoding = "ISO-2022-JP") {
    $string_array = array();
    $pos = 0;
    $row = 0;
    $mode = 0;
   
    while ($pos < mb_strlen($string)) {
        $word = mb_strimwidth($string, $pos, 1);
        if (!$word) {
            $word = mb_strimwidth($string, $pos, 2);
        }
        if (mb_ereg_match("[ -~]", $word)) {    // ascii
            if ($mode != 1) {
                $row++;
                $mode = 1;
                $string_array[$row] = NULL;
            }
        } else {                                // multibyte
            if ($mode != 2) {
                $row++;
                $mode = 2;
                $string_array[$row] = NULL;
            }
        }
        $string_array[$row] .= $word;
        $pos++;
    }
   
    //echo "<pre>";
    //print_r($string_array);
    //echo "</pre>";
   
    foreach ($string_array as $key => $value) {
        $value = mb_convert_encoding($value, $encoding);
        $string_array[$key] = mb_encode_mimeheader($value, $encoding);
    }
   
    //echo "<pre>";
    //print_r($string_array);
    //echo "</pre>";
   
    return implode("", $string_array);
}

is not the best, but it works
up
-3
mortoray at ecircle-ag dot com
17 years ago
At least for Q encoding, this function is unsafe and does not encode correctly. Raw characters which appear as RFC2047 sequences are simply left as is.

Ex:

mb_encode_mimeheader( '=?iso-8859-1?q?this=20is=20some=20text?=' );

returns '=?iso-8859-1?q?this=20is=20some=20text?='

The exact same string, which is obviously not the encoding for the source string.  That is, mb_encode_mimeheader does not do any type of escaping.

That is, the following condition is not always true:
    mb_decode_mimeheader( mb_encode_mimeheader( $text ) ) == $text
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官方地址：https://www.php.net/manual/en/function.mb-encode-mimeheader.php

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