Encodes MIME/HTTP header values that contain incorrectly encoded characters.
For example, mime_header_encode('tést.txt') returns "=?UTF-8?B?dMOpc3QudHh0?=".
See http://www.rfc-editor.org/rfc/rfc2047.txt for more information.
Notes:
$string: The header to encode.
string The mime-encoded header.
function mime_header_encode($string) {
if (preg_match('/[^\\x20-\\x7E]/', $string)) {
$chunk_size = 47;
// floor((75 - strlen("=?UTF-8?B??=")) * 0.75);
$len = strlen($string);
$output = '';
while ($len > 0) {
$chunk = drupal_truncate_bytes($string, $chunk_size);
$output .= ' =?UTF-8?B?' . base64_encode($chunk) . "?=\n";
$c = strlen($chunk);
$string = substr($string, $c);
$len -= $c;
}
return trim($output);
}
return $string;
}