Description:
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This was reported in the tips section for this function, but I didn't find it in the bug database.

The encoded text uses hex to represent escaped characters (e.g. "=3F" means the '?' character). RFC 2047 says that these hex digits can be either in upper or lower case. However, this function fails to convert them if the hex character is specified in lower case.



Reproduce code:
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echo mb_decode_mimeheader("Works: =?iso-8859-1?q?=3F=3F=3F?=");
echo "\n";
echo mb_decode_mimeheader("Fails: =?iso-8859-1?q?=3f=3f=3f?=");


Expected result:
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Works: ???
Fails: ???


Actual result:
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Works: ???
Fails: =?iso-8859-1?q?=3f=3f=3f?=