Description:
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I'm testing PHP 7.3.0RC2 (cli) (built: Oct  1 2018 11:46:48) ( NTS ) Ondrej's PPA on Ubuntu 18.04. It looks like conversion to/from UTF7-IMAP encoding is broken. See simple test script. It works as expected on PHP <= 7.2.



Test script:
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$str = '&BCAEMARBBEEESwQ7BDoEOA-';
echo mb_convert_encoding($str, 'UTF-8', 'UTF7-IMAP') . "\n";
$str = 'Рассылки';
echo mb_convert_encoding($str, 'UTF7-IMAP', 'UTF-8') . "\n";

Expected result:
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Рассылки
&BCAEMARBBEEESwQ7BDoEOA-


Actual result:
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BCAEMARBBEEESwQ7BDoEOA-
 0AAK;:8