解码mime邮件的代码

function decode_mime_string ($string) {
$pos = strpos($string, "=?");
if (!is_int($pos)) {
return $string;
}

$preceding = substr($string, 0, $pos); // save any preceding text

$search = substr($string, $pos+2, 75); /* the mime header spec says this is the longest a single encoded word can be */
$d1 = strpos($search, "?");
if (!is_int($d1)) {
return $string;
}

$charset = substr($string, $pos+2, $d1);
$search = substr($search, $d1+1);

$d2 = strpos($search, "?");
if (!is_int($d2)) {
return $string;
}

$encoding = substr($search, 0, $d2);
$search = substr($search, $d2+1);

$end = strpos($search, "?=");
if (!is_int($end)) {
return $string;
}

$encoded_text = substr($search, 0, $end);
$rest = substr($string, (strlen($preceding . $charset . $encoding . $encoded_text)+6));

switch ($encoding) {
case "Q":
case "q":
$encoded_text = str_replace("_", "%20", $encoded_text);
$encoded_text = str_replace("=", "%", $encoded_text);
$decoded = urldecode($encoded_text);

if (strtolower($charset) == "windows-1251") {
$decoded = convert_cyr_string($decoded, "w", "k");
}
break;

case "B":
case "b":
$decoded = urldecode(base64_decode($encoded_text));

if (strtolower($charset) == "windows-1251") {
$decoded = convert_cyr_string($decoded, "w", "k");
}
break;

default:
$decoded = "=?" . $charset . "?" . $encoding . "?" . $encoded_text . "?=";
break;
}

return $preceding . $decoded . decode_mime_string($rest);
} // decode_mime_string()