Encoding problems when sending @mail in PHP

Recently I ran into a problem, when sending gMail messages (and others too), could not correctly display my letter written by Cyrillic.
Climbed on the Internet, there this question has already been raised, and a solution was proposed. After reworking it for myself, I decided to put it here too. I think that some of you may find it useful too:

// The trim function removes spaces at the beginning and end
$ title = htmlspecialchars (trim ($ _ POST ['title']));
$ mess = htmlspecialchars (trim ($ _ POST ['mess'));

// Conversion
$ title = '=? koi8-r? B?'. base64_encode (convert_cyr_string $ title, "w", "k")). '? =';
$ to = 'some_main@gmail.com';
$ head = "Content-Type: text / plain; \ r \ n";
$ head. = "X-Mailer: PHP /". phpversion (). "\ r \ n";
$ head. = "Reply-To: admin@gmail.com \ r \ n";
$ head. = "To: $ name <$ to> \ r \ n";
$ head. = "From: admin@gmail.com \ r \ n";
$ head. = "Subject: $ title \ n";
')
// send
mail ($ to, $ title, $ mess, $ header);

Shl. I hope it will come in handy!