Base64_decode how to fix bugs?

Question

PHP

The point is simple.
I take the message from the mail via imap_open().

$header = imap_header($mbox, $msgno);  //Достаю заголовок
$subject = $header->subject;

As a result, the header of the letter is encoded in base64:
=?UTF-8?B?RndkOiDQn9C+0YHRgtGD0L/Qu9C10L3QuNC1INC90LAg0YHRh9C10YI=?=
When decoded, bugs come out.
If you use a service like online-decoder.com, then everything decodes perfectly with the mark (BASE64->UTF-8)
The page itself, where echo is done in utf-8.
And the same phrase when translated back to base64:
0J/QvtGB0YLRg9C/0LvQtdC90LjQtSDQvdCwINGB0YfQtdGC
Where is my cant? or what am I missing?

Answer 1

imap_utf8()
imap_mime_header_decode()

Answer 2

The '=' sign in base64 may be only at the very end, one or two, depending on the end of the triad, or may not be.
Characters '?' there shouldn't be a question.
Based on your line, try to cut off the text between the question marks - in my opinion, they are the ones that separate the desired text.