Description:
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If imap_fetchstructure encounters a message which contains an invalid sequence in a header field it somehow creates a deferred exception which is thrown on exit and is *not* caught by the handler defined in set_exception_handler.

I have not been able to produce an exact reproduction but I can confirm:
-the global exception handler is normally working
-it is something that imap_fetchstructure is doing -- if I remove this line it doesn't happen
--furthermore, it only seems to happen if one of the headers in the email has an invalid sequence: no encoding specified and contains a non-ascii character -- one which doesn't appear to be a valid latin1 character either


Expected result:
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I'm not expecting any exception to be thrown, but if one is (due to a class destructor exception) I'd expect it to be caught by the default exception handler.

Actual result:
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Just before PHP exits (after the script is finished) the following error:

error_handler(): [8] Unknown: Missing parameter (errflg=3) in Unknown at line 0

Fatal error: Exception thrown without a stack frame in Unknown on line 0