Description:
------------
mime_content_type() and finfo reports mime type application/octet-stream for MP3 files with ID3v1 tags. ID3v1 seems to be used in up to 10% of all MP3 files which have any ID3 tags.

This seems to be an issue with PHP built in magic.mime. Using a custom magicfile with finfo with just the below contents reports the mime type for those files correctly.

For the avoidance of doubt file -i also reports the wrong mime type unless I add the rows below to /etc/magic, so this might actually be an upstream bug.
id3v1.mp3: application/octet-stream; charset=binary

# for the test script the following is the file 'mp3id3v1_magic.mime'.
0       string      ID3     audio/mpeg
!:mime  audio/mpeg

Test script:
---------------
<?php
echo mime_content_type('id3v1.mp3') . "\n";

$finfo = new finfo(FILEINFO_MIME_TYPE);
echo $finfo->file($filePath) . "\n";

$finfo = new finfo(FILEINFO_MIME_TYPE, 'mp3id3v1_magic.mime');
echo $finfo->file($filePath) . "\n";

Expected result:
----------------
audio/mpeg
audio/mpeg
audio/mpeg

Actual result:
--------------
application/octet-stream
application/octet-stream
audio/mpeg