iconv_mime_encode

(PHP 5, PHP 7, PHP 8)

iconv_mime_encode — Composes a MIME header field

说明

iconv_mime_encode ( string $field_name , string $field_value , array $options = [] ) : string|false

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.

参数

field_name

The field name.

field_value

The field value.

options

You can control the behaviour of iconv_mime_encode() by specifying an associative array that contains configuration items to the optional third parameter options. 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	int	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

返回值

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

范例

Example #1 iconv_mime_encode() example


<?php
$preferences = 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);
?>

参见

imap_binary() - Convert an 8bit string to a base64 string
mb_encode_mimeheader() - 为 MIME 头编码字符串
imap_8bit() - Convert an 8bit string to a quoted-printable string
quoted_printable_encode() - 将 8-bit 字符串转换成 quoted-printable 字符串

User Contributed Notes

shaman_master at list dot ru 19-Feb-2020 07:36


From mail(): Lines should not belarger than 70 characters.  Not 76 and not 72!

cedric at gn dot apc dot org 13-Mar-2012 03:54


iconv_mime_encode() isn't directly suitable for encoding headers which include "specials" as described in RFC 1522 s4 & s5, for example 

<?php

$mimeprefs = array ("scheme" => "Q",

                    "input-charset" => "utf-8",

                    "output-charset" => "utf-8",

                    "line-break-chars" => "\n");

$enc = iconv_mime_encode('From',  '"Réal Namé" <[email protected]>', $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:



<?php

$encoded = "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.)

markus AT birth MINUS online DOT de 19-May-2010 05:38


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".



<?php

$subject = '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",

);



echo '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.