PHP Manual: Encode string for MIME header

Description

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

Encodes a given string string by the MIME header encoding scheme.

Parameters

string: The string being encoded. Its encoding should be same as mb_internal_encoding.
charset: charset specifies the name of the character set in which string is represented in. The default value is determined by the current NLS setting (mbstring.language).
transfer_encoding: transfer_encoding specifies the scheme of MIME encoding. It should be either "B" (Base64) or "Q" (Quoted-Printable). Falls back to "B" if not given.
newline: newline specifies the EOL (end-of-line) marker with which mb_encode_mimeheader performs line-folding (a » RFC term, the act of breaking a line longer than a certain length into multiple lines. The length is currently hard-coded to 74 characters). Falls back to "\r\n" (CRLF) if not given.
indent: Indentation of the first line (number of characters in the header before string).

Return Values

A converted version of the string represented in ASCII.

Changelog

Version	Description
8.3.0	`NUL` (0) bytes are no longer dropped when encoded using Quoted-Printable encoding, but encoded as `=00`.
8.0.0	`charset` and `transfer_encoding` are nullable now.

Examples

Example #1 mb_encode_mimeheader example

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

The above example will output:

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

Notes

Note:
This function isn't designed to break lines at higher-level contextual break points (word boundaries, etc.). This behaviour may clutter up the original string with unexpected spaces.

mb_encode_mimeheader