PHP 7.4.3 released


(PHP 5, PHP 7)

iconv_mime_encodeComposes a MIME header field


iconv_mime_encode ( string $field_name , string $field_value [, array $preferences = NULL ] ) : string

Composes and returns a string that represents a valid MIME header field, which looks like the following:

Subject: =?ISO-8859-1?Q?Pr=FCfung_f=FCr?= Entwerfen von einer MIME kopfzeile
In the above example, "Subject" is the field name and the portion that begins with "=?ISO-8859-1?..." is the field value.



The field name.


The field value.


You can control the behaviour of iconv_mime_encode() by specifying an associative array that contains configuration items to the optional third parameter preferences. The items supported by iconv_mime_encode() are listed below. Note that item names are treated case-sensitive.

Configuration items supported by iconv_mime_encode()
Item Type Description Default value Example
scheme string Specifies the method to encode a field value by. The value of this item may be either "B" or "Q", where "B" stands for base64 encoding scheme and "Q" stands for quoted-printable encoding scheme. B B
input-charset string Specifies the character set in which the first parameter field_name and the second parameter field_value are presented. If not given, iconv_mime_encode() assumes those parameters are presented to it in the iconv.internal_encoding ini setting. iconv.internal_encoding ISO-8859-1
output-charset string Specifies the character set to use to compose the MIME header. iconv.internal_encoding UTF-8
line-length integer Specifies the maximum length of the header lines. The resulting header is "folded" to a set of multiple lines in case the resulting header field would be longer than the value of this parameter, according to » RFC2822 - Internet Message Format. If not given, the length will be limited to 76 characters. 76 996
line-break-chars string Specifies the sequence of characters to append to each line as an end-of-line sign when "folding" is performed on a long header field. If not given, this defaults to "\r\n" (CR LF). Note that this parameter is always treated as an ASCII string regardless of the value of input-charset. \r\n \n

Return Values

Returns an encoded MIME field on success, or FALSE if an error occurs during the encoding.


Example #1 iconv_mime_encode() example

= array(
"input-charset" => "ISO-8859-1",
"output-charset" => "UTF-8",
"line-length" => 76,
"line-break-chars" => "\n"
$preferences["scheme"] = "Q";
// This yields "Subject: =?UTF-8?Q?Pr=C3=BCfung=20Pr=C3=BCfung?="
echo iconv_mime_encode("Subject""Prüfung Prüfung"$preferences);

$preferences["scheme"] = "B";
// This yields "Subject: =?UTF-8?B?UHLDvGZ1bmcgUHLDvGZ1bmc=?="
echo iconv_mime_encode("Subject""Prüfung Prüfung"$preferences);

See Also

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User Contributed Notes 3 notes

cedric at gn dot apc dot org
7 years ago
iconv_mime_encode() isn't directly suitable for encoding headers which include "specials" as described in RFC 1522 s4 & s5, for example
= array ("scheme" => "Q",
"input-charset" => "utf-8",
"output-charset" => "utf-8",
"line-break-chars" => "\n");
$enc = iconv_mime_encode('From''"Réal Namé" <>', $prefs);
will wrongly attempt to encode the angle brackets.  To use the function in place of mb_encode_mimeheader(), instead you need to encode the words separately, removing the superfluous field name:

= "From: \"". preg_replace('/^:\s+/', '', iconv_mime_encode("", $real, $mimeprefs))."\" <$email>";

Also, values of "line-length" greater than 76 would be illegal under RFC 1522 and resulting encoded words may not be recognised.  (Not tested, but 72 would be safer.)
shaman_master at list dot ru
2 days ago
From mail(): Lines should not belarger than 70 characters.  Not 76 and not 72!
markus AT birth MINUS online DOT de
9 years ago
Looks like this function suffers from the same bug as mb_encode_mime() with long strings of non us-ascii characters. The function then returns false. This applies for utf-8 to utf-8 "conversion".

= 'Вы находитесь здесь: Главная > продукт';

$prefs = array(
'scheme' => 'Q',
'input-charset' => 'UTF-8',
'output-charset' => 'UTF-8',
'line-length' => 76,
'line-break-chars' => "\r\n",

'Original: ' . $subject . PHP_EOL;
$enc = iconv_mime_encode( 'Subject', $subject, $prefs );
var_dump( $enc );  // will show bool(false)

As a workaround, you could explode() the value on spaces and encode each word separately. Then remove the "Subject: " in front of the resulting strings and join() them with "\r\n " (don't forget the SPACE after the \n) as separator.
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