imap_mime_header_decode()

(PHP 4, PHP 5, PHP 7)

解码MIME头元素

说明

imap_mime_header_decode (string $text) : array

Decodes MIME message header extensions that are non ASCII text (see » RFC2047).

参数

$text

The MIME text

返回值

The decoded elements are returned in an array of objects, where each object has two properties,charsetandtext.

If the element hasn't been encoded, and in other words is in plain US-ASCII, thecharsetproperty of that element is set todefault.

范例

Example #1 imap_mime_header_decode() example

<?php
$text = "=?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <keld@example.com>";
$elements = imap_mime_header_decode($text);
for ($i=0; $i<count($elements); $i++) {
    echo "Charset: {$elements[$i]->charset}\n";
    echo "Text: {$elements[$i]->text}\n\n";
}
?>

以上例程会输出：

Charset: ISO-8859-1
Text: Keld Jørn Simonsen
Charset: default
Text:  <keld@example.com>

In the above example we would have two elements, whereas the first element had previously been encoded with ISO-8859-1, and the second element would be plain US-ASCII.

参见

• imap_utf8()Converts MIME-encoded text to UTF-8

A nice way to decode strings is to use the mb_list_encodings(), but I had two problems with it: 
sometimes, the charset is uppercase in the header an lowercase in mb_list_encodings() and sometimes, the charset is not in the mb_list_encodings() list.
<?php
function upperListEncode() { //convert mb_list_encodings() to uppercase
  $encodes=mb_list_encodings();
  foreach ($encodes as $encode) $tencode[]=strtoupper($encode);
  return $tencode;
  }
function decode($string) {
  $tabChaine=imap_mime_header_decode($string);
  $texte='';
  for ($i=0; $i<count($tabChaine); $i++) {
    
    switch (strtoupper($tabChaine[$i]->charset)) { //convert charset to uppercase
      case 'UTF-8': $texte.= $tabChaine[$i]->text; //utf8 is ok
        break;
      case 'DEFAULT': $texte.= $tabChaine[$i]->text; //no convert
        break;
      default: if (in_array(strtoupper($tabChaine[$i]->charset),upperListEncode())) //found in mb_list_encodings()
            {$texte.= mb_convert_encoding($tabChaine[$i]->text,'UTF-8',$tabChaine[$i]->charset);}
           else { //try to convert with iconv()
             $ret = iconv($tabChaine[$i]->charset, "UTF-8", $tabChaine[$i]->text);  
             if (!$ret) $texte.=$tabChaine[$i]->text; //an error occurs (unknown charset) 
             else $texte.=$ret;
            }          
        break;
      }
    }
    
  return $texte;  
  }
?>

This function does not code a-z 0-9 like the function posted by bandpay at hotmail dot com
function encode_iso88591($string) {
  if( ereg("[^A-Za-z0-9\ ]", $string) ) {
    $text = "=?iso-8859-1?q?";
    for( $i = 0 ; $i < strlen($string) ; $i++ ) {
      if( ereg("[^A-Za-z0-9]", $string[$i]) ) {
        $text .= "=".dechex(ord($string[$i]));
      } else {
        $text .= $string[$i];
      }
    }
    return $text."?=";
  } else   return $string;
}

In response to Sven dot Dickert at planb dot de: if you encounter problems with "=?utf-8?Q?" appearing in your headers, I found that simply using "imap_utf8($string)" decoded the "$string" properly and solved my problem perfectly.

Here's a "flatMimeDecode" version converting UTF-8 to iso-8859-1:
function flatMimeDecode($string) {
    $array = imap_mime_header_decode ($string);
    $str = "";
    foreach ($array as $key => $part) {
      if($part->charset == "UTF-8"){
      $str .= utf8_decode ($part->text);
      }else{
      $str .= $part->text;
      }
    }
    return $str;
  }

Beware of multilined subjects containing whitespaces which are not part of the subject itself, but needed as functional characters for the clients.
i.e. you can have a mail header containing content like
Subject: =?iso-8859-1?Q?WG=3A_Mobilit=E4t_verschlechtert_--=3E_174?=
  =?iso-8859-1?Q?6?=
(carriage return and tabspace).
imap_mime_header_decode returns 5 parts (and not expected 2)
for this example.
- The first containing the space between "subject:" and the subject itself.
- The second is the first encoded text
- The third will be the line-break within the head lines.
The were inserted to keep rfc compliant line length and are NOT part of the original subject entered by the sender.
- The fourth will be the second part of the subject.
- The fifth is a line break - the last character will be a line break any time other head lines or mailbody will follow, so it's needed in the head - but not part of the original subject.

The example of diego is working well, he has a (very) little
mistake in his code. Here is the corrected version:
<?php
//return supported encodings in lowercase.
function mb_list_lowerencodings() { $r=mb_list_encodings();
 for ($n=sizeOf($r); $n--; ) { $r[$n]=strtolower($r[$n]); } return $r;
}
// Receive a string with a mail header and returns it
// decoded to a specified charset.
// If the charset specified into a piece of text from header
// isn't supported by "mb", the "fallbackCharset" will be
// used to try to decode it.
function decodeMimeString($mimeStr, $inputCharset='utf-8', $targetCharset='utf-8', $fallbackCharset='iso-8859-1') {
 $encodings=mb_list_lowerencodings();
 $inputCharset=strtolower($inputCharset);
 $targetCharset=strtolower($targetCharset);
 $fallbackCharset=strtolower($fallbackCharset);
 $decodedStr='';
 $mimeStrs=imap_mime_header_decode($mimeStr);
 for ($n=sizeOf($mimeStrs), $i=0; $i<$n; $i++) {
  $mimeStr=$mimeStrs[$i];
  $mimeStr->charset=strtolower($mimeStr->charset);
  if (($mimeStr == 'default' && $inputCharset == $targetCharset)
   || $mimStr->charset == $targetCharset) {
   $decodedStr.=$mimStr->text;
  } else {
   $decodedStr.=mb_convert_encoding(
    $mimeStr->text, $targetCharset,
    (in_array($mimeStr->charset, $encodings) ?
     $mimeStr->charset : $fallbackCharset)
    )
   );
  }
 } return $decodedStr;
}
?>

The previous comment (from hans) seems to make no sense at all, since it will not change the encoding and possibly result in a "multiencoding" string (that the browser and anything else will be unable to render, of course).
  I use a little function to decode the whole header to a specified encoding. It is as follow:
<?php
//return supported encodings in lowercase.
function mb_list_lowerencodings() { $r=mb_list_encodings();
 for ($n=sizeOf($r); $n--; ) { $r[$n]=strtolower($r[$n]); } return $r;
}
// Receive a string with a mail header and returns it
// decoded to a specified charset.
// If the charset specified into a piece of text from header
// isn't supported by "mb", the "fallbackCharset" will be
// used to try to decode it.
function decodeMimeString($mimeStr, $inputCharset='utf-8', $targetCharset='utf-8', $fallbackCharset='iso-8859-1') {
 $encodings=mb_list_lowerencodings();
 $inputCharset=strtolower($inputCharset);
 $targetCharset=strtolower($targetCharset);
 $fallbackCharset=strtolower($fallbackCharset);
 $decodedStr='';
 $mimeStrs=imap_mime_header_decode($mimeStr);
 for ($n=sizeOf($mimeStrs), $i=0; $i<$n; $i++) {
  $mimeStr=$mimeStrs[$i];
  $mimeStr->charset=strtolower($mimeStr->charset);
  if (($mimeStr == 'default' && $inputCharset == $targetCharset)
   || $mimStr->charset == $targetCharset) {
   $decodedStr.=$mimStr->text;
  } else {
   $decodedStr.=mb_convert_encoding(
    $mimeStr->text, $targetCharset,
    (in_array($mimeStr->charset, $encodings) ?
     $mimeStr->charset : $fallbackCharset)
    )
   );
  }
 } return $decodedStr;
}
?>
  Hope it helps.

Beware! imap_mime_header_decode in 4.0.6 is _not_ RFC2047 conform. The string =?utf-7?Q?Petra_M+APw-ller?= will not converted into Petra Mller cause the charset utf7 is unknown. Same goes to =?utf-8?Q?Petra_M=C3=BCller?= for charset utf8.

If you have errors with wrong attachment names like this:
correct name:
String -> Prüfbericht Hersteller.pdf
fetchstructure object name:
 =?ISO-8859-1?Q?Pr=FCfbericht_Hersteller=2Epdf?=
Workaround to reconvert:
imap_mime_header_decode($fetchstructure->dparameters->value)[0]->text
imap_mime_header_decode($filename)[0]->text

<?php
function decode_iso88591($string){
 if (strpos(strtolower($string), '=?iso-8859-1') === false) {
  return $string;
 }
 $string = explode('?', $string);
 return strtolower($string[2]) == 'q' ? quoted_printable_decode($string[3]) : base64_decode($string[3]);
}
?>

imap_mime_header_decode, utf-7 and utf-8 problem, i solved the problem using below function. note that iconv function for code converting.
you must replace "EUC-KR" as iconv parameter with charset you want such as "iso-8859-1".
function mime_decode($s) {
 $elements = imap_mime_header_decode($s);
 for($i = 0;$i < count($elements);$i++) {
  $charset = $elements[$i]->charset;
  $text =$elements[$i]->text;
  if(!strcasecmp($charset, "utf-8") ||
    !strcasecmp($charset, "utf-7"))
  {
   $text = iconv($charset, "EUC-KR", $text);
  }
  $decoded = $decoded . $text;
 }
 return $decoded;
}

I wrote a simple ks_c_5601-1987(2byte)
encode
function encode_ksc5601( $string )
{
 $encode = base64_encode( $string );
 $text = "=?ks_c_5601-1987?B?";
 $text = $text.$encode."?=";
 return $text;
}

This is obvious, but nevertheless here is a "flat" version:
<?php  
private function flatMimeDecode($string) {
  $array = imap_mime_header_decode($string);
  $str = "";
  foreach ($array as $key => $part) {
    $str .= $part->text;
  }
  return $str;
}
?>