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

示例 #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

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User Contributed Notes 3 notes

down

cedric at gn dot apc dot org ¶

10 years ago


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" <user@example.com>', $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.)

down

shaman_master at list dot ru ¶

2 years ago


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

down

markus AT birth MINUS online DOT de ¶

12 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".

<?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.

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